188 PALEONTOLOGY OF NEW-YORK. 



246. 1. CYRTOLITES COMPRESSUS. 



Pl. XL. A. Figs. 2 a, b, c, d, e,f. 

 Reference Pliragmolites cmnpressus, Conrad, Ann. Geol. Report, 1838, p. 110. 



Discoidal ; volutions scarcely contiguous, very gradually enlarging, rounded on the sides, 

 sharply and profoundly carinated on the dorsal margin ; greatest diameter of the volutions 

 from the dorsal to the ventral side ; aperture scarcely expanded ; surface ornamented by 

 transverse, zigzag or abruptly undulating, elevated, subinibricating lamellae, and finer 

 transverse and longitudinal stria;. 



This very beautiful and unique species is readily distinguished by the undulating elevated 

 lamelhT, which mark the surface at more or less distant intervals. Every forward bend of 

 these lines is accompanied by a slight depression behind it, and every retral bend shows a 

 broad slightly elevated ridge behind. This character is not, however, always conspicuous, 

 but sometimes gives a nodulose appearance to the shell. The sharp dorsal carina fills a 

 narrow groove in the ventral side of the inner volutions, the sides of which are not other- 

 wise in contact. 



The Genus Phragmolites of Conrad ( ut supra) was founded upon this species, on the 

 supposition that it was septate internally, which is not true, as I have had opportunities of 

 examining the interior. The undulated lines are merely superficial, and rarely at equal 

 distances from each other in diflferent shells. The Genus Cyrtolites was organized by Mr. 

 Conrad for the reception of a species from the Hudson-river shales : that species, like the 

 present, is profoundly carinated ; the carina filling a groove in the ventral side of the 

 volutions, which are scarcely contiguous. The surface in both is peculiarly ornamented and 

 subnodulose, the volutions having a greater longitudinal than transverse diameter. I have 

 therefore removed this species from Phragmolites, and placed it imder Cyrtolites, the 

 typical species of which is C. ornatus. It maybe remarked, in this place, that these species 

 differ in essential characters from any of the BucANiiE, to which they are in some respects 

 allied. 



Fig. 2 a. Lateral view of a specimen, having the sinuous lamollse at the ordinary distance asunder. 

 Fig. 2 b. Dorsal view of the same. 



Fig. 2 c. Lateral view of a specimen, where the elevated lamellas are more distant. 

 Fig. 2 d. Lateral view of another, showing the lamellas closely arranged. 

 Fig. 2 e. A cast, which is smooth, with the exception of the elevated carina. 



Fig. 2/ A portion of the surface enlarged, showing the finer transverse and longitudinal striffi, aiid the 

 subnodulose appearance of the surface. 



Position and locality. This species occurs, in its greatest perfection, in the lower shaly 

 strata of the Trenton limestone at Middleville. It is found, also, in the higher crystalline 

 pnitof the rock at the same place; and, in the form of casts, in the higher crystalline 

 portions of the same rock at Watertown. 



