Box 14, Folder 3: Coal 1861

39

back, the ventral sides being slightly concave, giving a very obtusely quadrangular section to the volution, the lateral diameter of which is a little greater than the dorso-ventral diameter.

Septa concave, numerous, these being on the back, about six in the space equal to the lateral diameter at the same point. Siphuncle small, situated on the back of the volution, outer chamber very gradually expanding.

Surface marked by obscure undulating folds, which commence upon the vertical side of the volution, and arching backwards unite with those from the opposite side in low ridges which are bent backwards in a broad sinus upon the dorsum. Lines of growth parallel to the undulations cover the entire surface.

This species differs conspicuously from L. undatus of the Trenton limestone of New York in the much more closely arranged septa, those of that species being less than half the number in the same space where the diameter of the volution is the same.

Geological Formation and Locality. In the "Buff limestone" of the Trenton limestone group, at Beloit, Wisconsin, and Rockford Illinois.

The species is dedicated to T. D. Roberston, Esq., of Rockford.

GENUS CYRTOCERAS, GOLDFUSS. CYRTOCERAS WHITNEYI, (n. s.)

Description. Shell robust, elongate arcuate, somewhat rapidly tapering, laterally compressed, giving an eliptical section, the lateral diameter being equal to three-fourths the ventral diameter, outer chamber short, septa numerous, but little concave, and exteriorly are directed forward on the dorsum, more closely arranged towards the apex and generally becoming more distant as the shell expands towards the aperture. On one specimen at a point where ethe dorso-ventral diameter measures three-fourths of an inch there are twleve septa in the length of one inch on the dorsum, while in the outer part where the diameter is less than one inch and one-fourth, there are but six septa in the length of one inch.

The surface of the shell is exfoliated, but there are distinct traces of longitudinal ridges which are situated at about three times their diameter from each other. In another speimen preserving a portion of the shell, fine concentric lines of growth with more closely arranged longitudinal ridges are visible.

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Geological Formation and Locality. In the shales above the Galena limestone, on Makoqueta creek in Iowa, and also on the east side of the Mississippi River, the particular locality unknown.

Collector. Dr. Thomas Scott, of Dubuque, Iowa.

Dedicated to Prof. J. D. Whitney.

CYRTOCERAS NELEUS [M crossed out], (n. s.)

Description. Shell of small or medium size, very gradually expanding from the apex and strongly curved, transverse section circular, or sub-circular, very obtusely sub-angular on the back in casts, most ventricose on the ventro-lateral region. Septa closely but not evenly arranged, averaging about nine in a space equal to the transverse diameter of the shell, curving forward on the dersal side, their margins undulated especially towards the outer chamber where they become crowded. On the ventral side the septa have a broad advancing curve. The exposed surface of the septa show the greatest concavity a little on the ventral side of the centre. Siphuncle dorsal, comparatively large.

Surface marked by transverse, slightly undulating annulations, which are strongly and abruptly curved backwards on the dorsum. Diameter of large specimens five-eights of an inch.

This species differs from C. lamellosum, Hall, I847 - C. Halleanus, D'Orbigny, 1850 - C. Billingsi, Salter, 1859, (Canadian Organic Remains, Decade I.), not C. lamellosum of De Verneuil, 1842, in the more gradual and equal curvature, the much less rapid expansion, (the expansion being only one sixteenth of an inch in a length of one inch and a quarter), and in the position of the Siphuncle which is situated close to the dorsal side.

Geological Formation and Locality. In the "Buff limestone" at Beloit, and forty feet above the base of the Trenton limestone group, Platteville.

Collectors. T.J. Hale and James Hall.

CYRTOCERAS EUGIUM, (n. s.)

Description. Shell of medium size, strongly curved and very gradually expanding from the apex. Section oblate, very obtusely sub-angular on the back, rounded on the sides, and depressed convex on the ventral side, giving the form of section described, the transverse diameter of which is greater than the dorso-ventral diameter. Septa moderately convex,

41

gently curved forward on the dorsum, and nearly straight on the ventrum; the greatest concavity being a little on the ventral side of the centre. Seven septa measured on the back, occupy a space equal to the transverse diameter. Siphuncle small, dorsal.

Surface marked by concentric lines of growth.

This species is remarkable for the oblate, obtusely triangular section, and its very gradual depression towards the aperture, the amount of increase in a length of one and a half inches being scarcely more than one-tenth of an inch. In two specimens examined the septa are more distant and are not crowded towards the aperture as in the preceding species, nor are they bent forward on the ventral side. The siphuncle is proportionally smaller, and the specimens preserve no markings beyond the striae of growth.

The specimens are casts and imperfect, the largest one having a diameter of three-fourths of an inch.

Geological Formation and Locality. In the "Buff limestone" of the Trenton limestone group, at Beloit, Wisconsin. Collectors. T. J. Hale, James Hall.

CYRTOCERAS FOSTERI, (n. s.)

Description. Shell elongate arcuate, making less than a volution, gradually tapering to the apex, sharply rounded on the dorsum, and less abruptly on the ventral side, compressed laterally, giving an elliptical section. Septa closely arranged, somewhat deeply concave, strongly arched forward on the dorsum; the space occupied by fine septa on the back of the shell scarcely equalling the transverse diameter at the same point. Siphuncle near the dorsal margin.

Surface characters unknown.

There are sixteen septa in the space of an inch and a half from the outer chamber, the last one being a little more approximate. The transverse diameter near the outer chamber is three-fourths of an inch, and the outer chamber, which is preserved for the length of less than an inch, continues to have the same gradual expansion as the septate portion.

This species differs from the C. Whitneyi in its more gradual increase in size, in being less compressed laterally, and in having the septa more regularly arranged or not increasing in distance with the age of the shell. The septa are likewise much more arched forward upon the back than in that species. There are no evidences of longitudinal striae on the

42 cast or upon the enclosing matrix as in that one, and it is only in the general form that the two approach each other.

Dedicated to J. W. Foster, Esq.

Geological Formation and Locality. In limestone of the age of the Niagara group, near Chicago, III. Received from J. W. Foster, Esq.

CYRTOCERAS LOCULOSUM, (n. s.)

Descriptian [Description]. Shell robust, somewhat rapidly increasing in size and strongly curved, abruptly rounded on the dorsal and ventral sides and much compressed laterally, becoming distinctly bilobate towards the outer chamber from the deep rounded channel on each side, which is a little on the dorsal side of the middle.

In three specimens examined, the dorso-ventral diameter is nearly or quite twice as great as the transverse diameter in the outer portions of the shell, while on the older parts the the diameters are more nearly equal, and the depressions upon the sides scarcely marked. Septa moderately concave, numerous, and sometimes very much crowded, strongly undulated across the depressions on the sides; strongly arched forward and produced on the back, the number ranging from sixteen to twenty-four in the space of an inch upon the back, while on the ventral side they are sometimes barely separated.

Position of the siphuncle and surface characters of the shell unknown.

This species is quite distinct from any other known to me, in the numerous crowded septa and the strong depressions along the sides, which occur in three specimens in the same relative position. The specimens are casts in Magnesian limestone, and no remains of the surface markings are preserved.

Geological Formation and Locality. In limestone of the age of the Trenton group of New York, at Madison, Wisconsin.

Collector. T. J. Hale.

CYRTOCERAS ORCAS, (n. s.)

Description. Shell robust, moderately curved, rapidly expanding from the apex to the beginning of the outer chamber, beyond which it is greatly contracted towards the aperture. One imperfect specimen of this species increases in its transverse diameter from seven-eighths of an inch to one inch and seven-eights [eighths] in a length of two inches. The section is transversely oval, the diameter being as ten to eleven and a half. Septa moderately concave, distant, from five to six in a space

43 equal to the transverse diameter of the specimen at the same point; having a broad, shallow, retral undulation on the dorsal side. Siphuncle dorsal small where it passes through the septa, and enlarging within the chambers.

Surface longitudinally striated.

This species is readily recognized, and distinguished from any others in the same association by its great expansion, and by its distant septa, as well as in having the transverse diameter greater than the dorso-ventral diameter. Length from for to six inches or more.

Geological Formation and Locality. In limestone of the age of the Niagara group, Racine, and at Waukesha, Wisconsin.

CYRTOCERAS DARDANUS, (n. s.)

Description Shell robust, strongly curved, moderately expanding from the apex, and slightly contracting near the aperture; transverse section broadly elliptical, the greater diameter in a dorso-ventral diameter. Dorsal and ventral sides equally rounded. Septa distant, measuring only four in a distance equal to their transverse diameter, deeply concave, and strongly arched forward on the dorsum. The siphuncle of moderate size, dorsal.

Surface apparently smooth or with only lines of growth, the small remains of the shell showing with no markings. The length of entire individuals has been from six to eight inches.

The specimens examined are casts of imperfect individuals, but they are so well marked as to be easily recognized.

Geological formation and locality. In limestone of the age of the Niagara group, at Waukesha, Wisconsin.

GENUS ONCOCERAS, HALL.

In the first volume of the Palalontology [Paleontology] of New York, I have proposed a separation of the forms like Cyrtoceras, when the aperture is abruptly constricted, and the apex more abruptly tapering from the middle of the shell. Some of the forms are much like curved Gomphoceras, with a more extended apex. The section is usually broadly elliptical and the siphuncle dorsal, or on the outer side of the curve.

The contradiction towards the aperture is often extreme, and in all individuals which I have seen, this feature is strongly marked. The genus is at least convenient for the reference of species of this peculiar type.