CLINTON GROUP. 



65 



Position and locality. In the upper green shale of The group, associated with Graptolithus 

 clintonensix, at Sodus bay, Wayne county. This shell is unknown beyond this locality. 



(State Collection.) 



172. 1. SPIRIFER* BIFORATUS, var. LYNX. 



Pl. XXII. Fig-, la-e. 

 For synonymy and references, see Pal. N. York, Vol. i, p. 132. 

 Delthyris brachynota. Rep. 4th Geol. Dist. N. York, 1843, p. 71 ; fig'. 6, p. 70. 



This shell is evidently identical with the D. lynx of the lower strata. M. de Verneuil has 

 suggested the analogy in his paper on the parallelism of American and European rocks, page 

 655 ; and he mentions having found fragments of the same shell in the Clinton group in Ohio. 

 All the specimens I have seen in this position are single valves, and so much worn as to pre- 

 sent no indication of the concentric undulating lamellae. There is no difficulty, however, in 

 identifying the shell, after being acquainted with D. lynx as it appears in the lower rocks. In 

 1843 I had seen no figure or description of D. lynx, and had then had no opportunity of 

 studying the species of the lower rocks which have since engaged my attention. 



The figures on Plate 22 give the usual appearance of this fossil, as it is found in the Clinton 

 group. 



Fig. 1 a. Ventral valve, with a very short hinge-line. There are four mesial plates, and twelve 

 or thirteen on each side. The great number of ribs on each side the mesial lobe is 

 remarkable, being greater than in any specimen I have ever seen. 



Fig. 1 b. The ventral valve of another specimen, having the mesial lobe worn smooth, and ten 

 ribs on each side. The hinge-line is somewhat more extended than in the preceding 

 specimen. 



Fig. 1 c. The dorsal valve of a large specimen, having four ribs in the mesial sinus, and ten 

 on each side. 



Fig. 1 d. The interior of the dorsal valve, showing the form of the muscular impression, and 

 the papillose surface on each side. 



Fig. 1 e. Cardinal view of the ventral valve, showing the projecting dental processes. 



Position and localities. This species occurs, associated with Pentamerus oblongus, at Ro- 

 chester ; and at Reynale's basin, Niagara county, associated with Atrypa congesta in the cal- 

 careous layers. M. de Verneuil mentions the occurrence of this species in the magnesian 

 limestone at Springfield, Ohio. {State Collection.) 



* There seems no good reason for adopting the term Delthyris instead of Spirifer, since the latter name has pre- 

 cedence in point of time, and since the typical species of Spirifer given by Sowerby are generically identical with 

 those given by Dalman as species of DelthyrLf. The latter name has besn adopted in this country to distinguish the 

 true types of the original genus Spirifer from the apparently heterogeneous assemblage of species included under 

 that genus by European authors. Hereafter in this work the name of Spirifer will be adopted in place of Delthyris. 

 [Palaeontology — Vol. ii.] 9 



