122 UNITED STATES GEOLOGICAL SUKVEY OF THE TEEEITOEIES. 



Since the foregoing description and remarks were in type, I have had 

 an opportunity to examine good specimens of the recent (Jouldia mactracea, 

 from our eastern coast, and find that it does not differ so widely as supposed 

 by Mr. Gabb, in the character of the posterior side of its hinge, from his 

 type. On the contrary, it certainly has a small, but unmistakable, remote 

 posterior lateral tooth in the left valve, that fits into a corresponding indenta- 

 tion under the edge of the opposite valve, just over the posterior muscular 

 scar; while this posterior edge of the right valve is beveled and prominent, 

 so as to fit into a long, slender, posterior marginal furrow in the left valve, as 

 a long posterior lateral tooth. Mr. Gabb, however, describes Eriphyla as 

 having an external ligament, of the existence of which I can see no traces in 

 Gouldia mactracea ; though, as might be expected from its affinities, it cer- 

 tainly has a well-developed internal cartilage, occupying the anterior half of 

 the comparatively large central pit in the right valve, and a smaller pit just 

 in front of the well-developed cardinal of the left. 



This larger pit between the two cardinal teeth of the right valve in G. 

 mactracea, has a low, slender, mesial ridge, separating its anterior half (occu- 

 pied by the cartilage) from the slightly narrower posterior part that receives 

 the cardinal tooth of the other valve. Anteriorly, the right valve has a long 

 marginal furrow, for the reception of a long tooth formed by the mere bevel- 

 ing and prominence of the anterior margin of the left valve ; while the lower 

 anterior edge, under this long furrow of the right valve, just over the anterior 

 muscular scar, projects as a single, remote, anterior lateral tooth. From these 

 remarks, it will be seen that in G. mactracea, at least, there are both anterior 

 and posterior lateral teeth, the posterior of which in the left valve, corresponds 

 in arrangement, and nearly in size, to the anterior in the right, and the ante- 

 rior in the right, to the posterior in the left, respectively. Consequently, with 

 the exception apparently of an external ligament in Eriphyla, that type would 

 appear to be quite closely related to Gouldia. 



Dr. Stoliczka refers three round, compressed Cretaceous shells, with but 

 slightly prominent beaks and a shallow pallial sinus, to Mr. Gabb's genus 

 Eriphyla. These Indian shells seem to agree pretty nearly in the more 

 essential generic characters of the hinge, excepting its greater breadth, with 

 the California type; but their lenticular form and very slightly prominent 

 beaks give them a very different aspect, suggesting, with their sinuous pallial 

 line, as remarked by Dr. Stoliczka, affinities to Dosinia; while, as already 



