INVERTEBRATE PALEONTOLOGY. .")L J :! 



Subgenus LEPTEOTHEO (see page 101). 

 Corbie u la subelliptica, M. & H. 



Plate 43, figs. 9, o,6,c. 

 Tcllina subellipHoa, Meek and Hoyden (185G), Proceed. Acad. Nat. Sci. Philad., VIII, 83. 



Shell small, compressed, transversely subelliptic, thin ; anterior margin 

 narrowly rounded, posterior faintly subtruncated ; base forming a semi- 

 elliptic or semi-ovate curve; beaks rather depressed and placed slightly in 

 advance of the middle, when not worn abruptly pointed; dorsal margin 

 sloping rather gradually from the beaks, the anterior slope being slightly 

 concave in outline, and the posterior nearly straight ; surface with only 

 obscure marks of growth; interior of valves 'showing an obscure ridge, 

 extending downward from the beaks, and leaving a corresponding shallow 

 sulcus on internal casts; muscular impressions well defined; pallial line with 

 a shallow, rounded sinus. 



Length of the type-specimen, 0.44 inch ; height, 0.32 inch ; convexity, 

 about 0.10 inch. 



Some casts from the original locality indicate a size about one-fourth 

 larger than that from which the above measurements were taken. 



The specimen represented by figure 9, a, of our plate 43, is the type of 

 this species. It gives no idea of the hinge or internal characters; and, as we 

 originally had no other fossils from the same locality and position, we had no 

 means of determining whether it came from a marine or brackish-water 

 formation ; but from its general external appearance supposed that it might 

 belong to some section of the genus Tellina, to which we referred it 

 provisionally. Subsequently, a few internal casts, from near the same 

 locality, and evidently belonging to the same species, were brought in; 

 and these at once showed that it cannot belong even to the Tellinidce, as it 

 has a very shallow pallial sinus. On cutting away some portions of the shell 

 remaining about the hinge of one of these casts, I found that it has the hinge- 

 teeth of Corbicula, or rather of the transverse section of that group, in which 

 the elongated lateral teeth are often nearly smooth, or but obscurely striated. 



The discovery of this fact led me to compare it with specimens of a very 

 similar form, that I have long had under consideration, from Bijou Creek, 

 Colorado; and on doing so they were found to be specifically identical* As 



* Associated with these Colorado specimens, two upper valves of an Anomia were found, which I 

 believe to be the same species that I have described under the name A. micronema, from a shaft on the 

 Kansas Pacific Railroad; at a locality two hundred miles east of Denver, Colorado. 



