188 
PALAEONTOLOGY OF NEW-YORIf. 
246. 1. CYRTOLITES COMPRESSUS. 
Pl. XL. A. Figs. 2 a, b , c, d, e, f. 
Reference Phragniolites compressus, Conrad, Ann. Geol. Report, 1838, p. 119. 
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, subimbricating lamellae, and finer 
transverse and longitudinal striae. 
This very beautiful and unique species is readily distinguished by the undulating elevated 
lamellae, 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 different 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 under 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 Bucanije, to which they are in some respects 
allied. 
Fig. 2 a. Lateral view of a specimen, having the sinuous lamellae at the ordinary distance asunder. 
Fig. 2 b. Dorsal view of the same. 
Fig. 2 c. Lateral view of a specimen, where the elevated lamellae are more distant. 
Fig. 2 d. Lateral view of another, showing the lamellae closely arranged. 
Fig. 2 c. A cast, which is smooth, with the exception of the elevated carina. 
Fig. 2 f. A portion of the surface enlarged, showing the finer transverse and longitudinal striae, and 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 
part of the rock at the same place ; and, in the form of casts, in the higher crystalline 
portions of the same rock at Watertown. 
