INVERTEBRATES. 507 



Genus LITUITES, Breyn. 



Lituites Graftonensis, M. and W. 



PI. 25, Fig. 1 . 

 Lituites Graftonensis, Meek and Worthen, 1S69. Proceed. Acad. Kat. Sci., Philad. 



Shell rather small, with the involuted portion discoid, planorbicular, 

 and slightly concave on both sides ; volutions four or more, slightly 

 embracing, increasing very gradually in size, with transverse section 

 nearly or quite circular, excepting the shallow concavity along the inner 

 side. Surface ornamented by numerous, distinct, very regularly 

 arranged costse, which cross the sides of the volutions very obliquely 

 backward from the inner side, curving strongly backward as they 

 approach the periphery, and after crossing the middle of the same, 

 again deflected abruptly forward as on the opposite side ; this indica- 

 ting a profound sinus in the outer side of the lip, the sinus being very 

 narrow, but not quite angular at its termination, and widening rapidly 

 forward ; fine, somewhat imbricating striae of growth also run parallel 

 to the costse. Septa apparently rather distant and running nearly 

 straight across the sides of the volutions. Siph ancle and free portion 

 of the outer volution unknown. 



Greatest diameter of the coiled part, 2.10 inches ; transverse diame- 

 ter, 0.54 inch ; dorso-ventral diameter of outer volution, 0.52 inch. 



As we have seen neither the siphuucle nor the free part of the body 

 chamber of this species, we cannot be positively sure it has exactly the 

 characters of the genus Lituites. Yet as it does not show the slighest 

 appearance of the obliquity of the volutions seen in Trochoceras, we 

 have scarcely any doubt in regard to its being a true Litulte. Com- 

 pared with Lituites Marshii, of Hall, (20th Aun. Eep. Regents' Univer- 

 sity N. Y. on State Cab. Nat. Hist., PI. 16, fig. 6, 7,) from the same 

 horizon at Kankakee in this State, our species will be found to differ in 

 having its volutions more compactly coiled together, much less rapidly 

 increasing in size, and ornamented with smaller and much more closely 

 arranged costse. Its costse also make a stronger, or deeper backward 

 curve, in crossing the periphery, which is rounded instead of being 

 flattened, as in the Marshii. This flattening along the outer side of the 

 whorls of L. Marshii, seems to indicate that it belongs to the subgenus 

 Ophidioceras of Barrande, while our species agrees, in the rounded char- 

 acter of its periphery, with the typical Lituites. 



In general appearance our shell is more likei. (Trocholites) ammomus, 

 of Conrad, from the Lower Silurian, though its costse are much more 

 oblique, and differ in being separated by rounded furrows quite as wide 



