156 PALAEONTOLOGY OF CALIFORNIA.. 



convex, most prominent anteriorly, and sloping upwards to the 

 posterior end nearly straight ; shell a little more than twice as 

 long as wide. Surface marked by numerous microscopic, con 

 centric lines, generally somewhat irregular. Muscular scars 

 deep ; pallial sinus broad, shallow. 



Figure, natural size. 



Localities: In Division B., near MartiSez; and abundant at Marsh's, fifteen 

 miles east of Mount Diablo. A single specimen was found at Alizos Creek, near 

 Fort Tejon. 



T. REMONDII, n. s. 



PL 22, Fig. 132. 



SHELL broad, thin, compressed, about a third longer than 

 wide; anterior end broadly rounded; posterior rostrate, nar 

 row, and truncated obliquely outwards and downwards; beaks 

 small, central, prominent; base broadly rounded, slightly sinu 

 ous near the posterior extremity; a well-marked ridge passes 

 from the beak to the posterior basal angle; cardinal margin 

 convex in front, concave behind the beaks, and sloping down 

 wards concavely towards the truncated posterior end. Surface 

 ornamented by numerous small, regular, concentric ribs, and by 

 smaller, radiating, interstitial lines. 



Figure, natural size. 



Locality : Two specimens from Cochran's, six miles east of Mount Diablo, col 

 lection of Mr. Re"mond; one from near Fort Tejon. 



T. HOFFMASTNTANA, n. 8. 

 PL 22, Fig. 133, and 133 a. 



SHELL moderate in size, compressed, a little longer than wide; 

 beaks nearly central, somewhat variable, prominent; cardinal 

 margin sloping each way, nearly straight, most abrupt poste 

 riorly ; anterior end broadly rounded, posterior produced, nar 

 row, rounded or sub truncate, and sometimes slightly reflected 

 laterally , basal margin convex, most prominent directly under 



