98 



PALEONTOLOGY OF NEW-YORK. 



INCERT^ SEDES. 



494. 1. CORNULITES FLEXUOSUS (n. 5^.). 



PL. XXVIII. Fig. \2a-e. 



Body an extremely elongated hollow cone, flexuous or arcuated, composed of a series of 

 rings with the edges placed one within the other ; each ring smaller at the base and expanding 

 above, the upper margin rounded and incurved so that the edge closely embraces the base of 

 the next succeeding ring ; the shell or crust at the base of each ring is thinnest, and gradually 

 becomes thicker at the same time that the diameter becomes greater ; surface of the external 

 crust cancellated by strong undulating strise, the longitudinal ones often obsolete. 



This very peculiar body, in the present state of our knowledge, is not referable to any 

 known type or family. The specimens which usually come under observation are imperfect ; 

 and the shell commonly remaining is evidently an internal shell, which has been encased within 

 another. This internal shell or crust is usually smooth, but there are sometimes single longitu- 

 dinal elevated lines at wide and unequal distances from each other ; these, where occurring, 

 scarcely interrupt the general smoothness of the surface, and more frequently they are absent 

 altogether. In several specimens there are portions of an exterior shell remaining upon the 

 inner one ; and in a single specimen, the entire exterior shell is preserved, somewhat worn, 

 but presenting an entirely different character from the usual aspect of this fossil. In this state 

 it likewise appears to be composed of a series of rings, but which are largest in the centre 

 and becoming thinner at either edge, the lower or larger enclosing within its upper edge the 

 base of the next succeeding one. The surface of these rings is strongly striated in a transverse 

 direction ; and in the less worn parts, longitudinal strise are distinctly visible. It is e\'ident, 

 from the condition of these specimens, that these rings were so joined as to admit of lateral 

 motion, since all the specimens are curved or tortuous, and this without having suffered any 

 great degree of pressure. The existence of an inner and an outer shell may perhaps be 

 explained, by supposing it to be a simple exfoliation of the outer portion ; but this seems 

 scarcely adequate to produce the effect, since the separation of the parts always leaves the 

 same form beneath, and the surface thus remaining has no marks of exfoliation. In the original 

 form the rings are not larger, above ; but the portion separating is always thinner at the upper 

 edge, and thicker at the lower or smaller diameter of the ring, so that its exfoliation leaves 

 the form represented in figures 12 c, d, e. On the other hand, the shell remaining is thinner 

 below and thicker above, as already described. 



Fig. 12 a. A specimen, somewhat tortuous in form and partially compressed, covered with the 



external striated shell. 

 Fig. 12 i. A portion of the surface enlarged. 

 Fig. 12 c. A specimen, nearly entire, exhibiting the usual form and surface characters of this 



fossil. 

 Fipf. 12 d. A fragment of a specimen more curved than usual. 



