﻿308 GABIi'S DESCRIPTIONS OF 



slightly incurved ; lower valve slightly convex and regularly curved from the beak 

 to the ba<al margin, shell wider than long ; hinge line apparently extended in a 

 point behond the shell ; surface marked by about fifteen rounded ribs crossed by 

 concentric lines; the ribs cover about three-fifth of the shell, leaving one-fifth at each 

 angle on both valves with only the concentric markings ; upper valve slightly concave, 

 very imperfect. The figure was inadvertently omitted by the lithographer. 

 Locality and position. — With the preceding. 



Rynciionella II alli. PI. 48, fig. 29, a, b, c. 



Shell subtriangular, inflated; lower valve, beak moderately large, curved over the 

 smaller valve, margin deeply sulcate, with a small rib in the centre of the sulcus, 

 three ribs on each side; upper valve with two ribs in front, corresponding with the 

 depression on the other vafve, three lateral ribs, the upper one very faint; the ribs 

 on both valves extend about half the width of the shell from the margin towards the 

 beaks, leaving the upper half of the shell plain ; surface marked by faint concentric 

 lines (crossed by very indistinct radiating lines in one specimen; the others do not 

 show this character.) 



This shell, with the others, was found by my friend Mr. Conrad, several years ago, 

 in Bath Co., Va. Mr. C. % is not able to tell me their relation to the coal of Vir- 

 ginia, but from their locality they could not have been far from it. Further investi- 

 gation will be necessary to determine whether they belong to a stratum above or 

 below the coal. However, they are interesting, since they serve to add another link 

 to the chain of facts that go to determine the age of this interesting deposit. The 

 great probability is that they are Triassic. This view has been held for some time by 

 Lyell, Rogers, Leidy and others. The genera above mentioned will not serve to 

 restrict the age of this formation to the Trias. The genus Ceratites confines it to the 

 Secondary group, but this genus is said to range to the top of the division. I have 

 carefully examined, as far as I have been able, all the figures of so-called Cretaceous 

 Ceratites, which the extensive library of the Academy would permit, and I have not 

 yet seen a figure but what has shown a more or less complex septum. I have been no 

 more sucessful with the Jurassic; still the evidence is only negative. 



This Ceratite is the first American fossil that could be referred without doubt to 

 this genus. If the C. Americanus of Harper should prove to be what, from the figure 

 in the Proceedings of the Academy, it appears to be, — a weathered specimen of an 

 Ammonite — then our species will be the first one found in America. I am inclined to 

 this opinion the more strongly from the fact that I have before me a very much worn 

 specimen of a A. Delawarensis, from Alabama, so nearly resembling the figure above 

 quoted as hardly to be distinguished from it. 



