310 GEOLOGICAL SUKVEY OF THE TEKRITORIES. 



This shell will be readily distinguished from the Tellinas of our cre- 

 taceous rocks by its shorter, slightly more convex, subtrigonal, or sub- 

 ovate nearly equilateral form, even where its hinge cannot be seen. In 

 some respects it looks externally like a compressed and depressed Mac- 

 tra. I am unacquainted with any tertiary species with a similar hinge. 



Locality and position : Twelve miles southwest of Salina, Saline 

 County, Kansas ; Dakota Group of Upper Missouri cretaceous. Profes- 

 sor B. F. Mudge. 



TELLINA SUBSCITTJLA, (MEEK.) 



Shell small ; elliptic-suboval, much compressed ; pallial margin form- 

 ing a regular semi-elliptic curve : extremities narrowly rounded, the pos- 

 terior being a little shorter, with a very obscure flexure, and more ab- 

 ruptly or narrowly rounded below ; dorsal outline sloping gently in both 

 directions from the beaks, the posterior slope being a little convex in 

 outline, and the anterior nearly straight ; beaks depressed, compressed 

 and placed a little behind the middle ; muscular impressions moderately 

 distinct, the posterior one being broader than the other ; pallial sinus 

 very deep, nearly horizontal, and rather broadly rounded. Surface with 

 only fine lives of growth. 



Length, 0.84 inch ; height, 0.47 inch ; convexity, about 0.15 inch. 



This shell is much like Tellina scitula, M. and H., from the upper mem- 

 ber of the Upper Missouri cretaceous series ; but on comparison it is 

 found to be proportionally more depressed, while its pallial sinus is very 

 different, being much broader and more obtusely rounded at the end. 

 Impressions of its surface in the matrix also indicate less strongly-de- 

 fined lines of growth. Casts show that it has no lateral teeth. 



Locality and position : Same as last. Professor Mudge. 



TAPES WYOMINGENSIS, (MEEK.) 



Shell elongate-subelliptic in outline, much compressed; extremities 

 nearly equally rounded ; pallial margin straight and nearly parallel to 

 the dorsal, but rounding up regularly at both ends ; dorsal side straight, 

 or very slightly convex in outline ; beaks depressed nearly or quite to 

 the dorsal margin, and placed about one-fourth the length of the valves 

 from the anterior end ; anterior muscular impression ovate, rather well 

 defined, and with- its longer diameter ranging vertically ; pedal scar 

 distinct near the upper end of that of the anterior adductor ; posterior 

 muscular impression very shallow; pallial line with its sinus rather 

 deep, horizontal, and obtuse at the end. Surface with lines and some 

 small ridges of growth. 



Length, 1.70 inches ; height, 0.82 inch ; convexity, about 0.28 inch. 



The only specimens of this species yet obtained are mainly casts re- 

 taining some portions of the shell. They give very little idea of the 

 nature of the hinge beyond the fact that it seems to have three diverging 

 cardinal teeth, the exact form and arrangement of which cannot be 

 made oat. The general expression of the shell, however, is very nearly 

 that of some European cretaceous forms that seem to have essentially 

 the hinge characters of Tapes, though they may not be exactly congeneric 

 with the recent species of that genus. Among the foreign species our 

 shell seems to be most nearly represented by Venus fragilis, d'Orbigny 

 (from the cretaceous of Prance), which is not a true Venus, but has been 

 referred by Mr. Zittel to the genus Tapes. (See Bivalven der Gosaug., 

 jSord Alpen.) 



