CRETACEOUS FOSSILS. 135 



T. Saffordii, Gabb. 



PI. 21, Fig. 93. 



(T. Saffordii, G. ; Journ. Acad. Nat. Sci. Phila. 2 ser., vol. 4, p. 392, pi. C8, fig. 

 12 (11 in text, per err.) 



Shell elongated, many-whorled (about fourteen in the largest 

 specimen) ; whorls increasing very gradually in size, flattened 

 or concave on the side, and bevelled above and below ; suture 

 impressed. "YVhorls marked by a variable number of small re- 

 volving lines, which are sometimes obsolete on a part, and some- 

 times on the whole surface ; besides these, there are sinuous 

 lines of growth. Mouth subquadrate, rounded on the angles. 



Figure, natural size. 



Localities: Six miles northeast of Suisun, Solano County; south of Clear Lake, 

 Lake County. The latter collected by Dr. Veatch. Also near Martinez (Divi- 

 sion A.). 



This species is the largest Cretaceous Twritella of California, and can be readily 

 recognized, even in casts, by its size. The surface-markings are somewhat va- 

 riable. In the Tennessee form there were distinct lines on the under side of 

 the whorl, when those on the sides were obsolete. In the Suisun specimen the 

 whole surface is strongly marked ; while in the older specimens from Clear Lake 

 the revolving striae are entirely wanting, but are found on the younger whorls. 

 In this case, too, there are well-marked undulations parallel with the lines of 

 growth, which are most prominent on the angles of bcvelment. 



T. robusta, n. s. 



PI. 21, Fig. 94. 



Shell conical, robust; whorls increasing rather rapidly in size, 

 convex ; suture linear. Surface marked by four rather promi- 

 nent, revolving ribs, with concave interspaces; the upper one 

 is placed some distance from the top of the whorl, with a broadly 

 concave space between; the others are placed at about equal 

 distances, the lower one being on the under side of the whorl ; 

 of these, only two are visible on the upper whorls. Aperture, 

 unknown. 



