TRENTON LIMESTONE. 
193 
There may be some doubt as to the propriety of separating this species from Lituites, 
which has been clone principally on account of the ventral position of the siphuncle ; since 
this deviation is not usually regarded as important. M. de Verneuil, speaking of this 
position of the siphuncle in L. odini, does not consider it as sufficient to found a generic 
distinction. 
Fig. 4 a. A small perfect specimen, showing the lamellose striae in great perfection. 
Fig. 4 b. A large specimen, preserving the lamellose surface. 
Fig. 4 c. Dorsal view, showing the archings of the striae upon the back. 
Fig. 4 d. A specimen denuded of the shell, showing the septa and deep outer chamber. 
Fig. 4 e. Section, showing the position of the siphuncle. 
Fig. 4 f g. Lateral and dorsal view of a fragment of an inner volution, showing a slight undulation of 
the septa on the back. 
Fig. 4 h. Lateral view of a fragment partially denuded of the shell, showing only the oblique transverse 
ridges. 
Fig. 4 i. Dorsal view of the same, showing the arching of the striae upon the back. 
Fig. 4 k. Section of the same, showing the position of the siphuncle. 
Position and locality. This shell occupies a central position in the Trenton limestone, 
being unknown in the lower part, but passing upwards into the Utica slate, where it is of 
less frequent occurrence. ( State Collection.) 
250. 1. CYRTOCERAS LAMELLOSUM (n. sp.). 
Pl. XLI. Figs. 2 a, b, c. 
Subcylindrical, gradually curving and tapering ; aperture somewhat expanded, and the 
shell slightly constricted just behind ; septa closely arranged ; surface with transverse 
undulating squamose lamellae, which are abruptly bent backwards on the dorsal line ; 
lamellae equidistant with the septa, but not corresponding to them ; spaces between the 
lamellae marked by fine transverse striae. 
The form of the entire shell is unknown, the only specimen seen being a fragment : 
this, however, is well characterized in its surface markings, which resemble in some 
degree those of the Cyrtolites compressas ; but the lamellae are more squamose, and less 
abruptly undulating, as well as more closely arranged than is usual in that species. An 
exfoliation of the shell on one side exposes the interior, which is clearly septate. 
Fig. 2 a. Lateral view of the fragment 
Fig. 2 b. Dorsal view of the same. 
Fig. 2 c. Magnified portion of the surface. * 
Position and locality. In the lower part of the Trenton limestone at Middleville. 
[ Palaeontology.] 
25 
