IHVERTEBEATB PALEONTOLOGY. 125 



Our shell shows, just behind and partly between (he beaks, a minute 

 furrow above the hinge in each valve, defining what has all the appearances of 

 a fulcrum for the attachment of a very small, external ligament (see f, of fore- 

 going cuts); in which character it would agree with Mr. Gabb's description 

 of Eriphyla. But in this, as well as in the relative positions of its cardinal 

 teeth of the opposite valves, it differs from Gouldia mactracea. I do not know, 

 however, how far Gouldia may vary in the arrangement of its hinge-teeth; 

 but certainly in G. matracea (as already stated), the two well-developed 

 cardinal teeth are in the right valve, and the single oue in the left; while in 

 the published figures of G. Pacifica the same arrangement is shown. Dr. 

 Stoliczka, however, defines that genus (whether from recent or fossil species 

 he does not say) as having "one cardinal tooth in the right valve and two 

 in the left," exactly as in our shell ; while his figure of an Indian Cretaceous 

 species shows, apparently, the same arrangement mentioned in his generic 

 description. 



In the present state of our knowledge of the affinities and range of 

 variation of these little Cretaceous types, I am left in some doubt in regard 

 to the proper disposition of our shell, but have concluded to refer it provis- 

 ionally to Eriphyla for the present. If the existing species of Gouldia vary 

 in the relative arrangement of the cardinal teeth in the two valves, possibly 

 I would be nearer right to call our shell Gouldia gregaria; but if they are 

 constant in this character, and further comparison should show our shell 

 to be generically distinct from Eriphyla, I would propose for it the name 

 Eripliylopsis. 



In first describing this species, little or nothing was known of its hinge, 

 and it was referred to Aslarte from external characters only. On subsequently 

 taking it up for more thorough study, however, and sacrificing some of the 

 best specimens in cutting about the hinge, the characters here given were 

 revealed. 



Specifically, this little shell may be compared with Aslarte similis, 

 Minister, as figured by Dr. Zittel in his valuable Monograph of the Bivalves 

 of the Gosau formation, with which it seems to agree very nearly in size 

 and form. It differs, however, in having much smaller and more numerous 

 concentric undulations and a more rounded outline. I am not accpiainted 

 with the hinge of Minister's species, but it is very probably not a true Astarte. 

 Another Gosau species, figured on the same plate by Dr. Zittel under the name 



