CRETACEOUS FOSSILS. 59 



NAUTILUS, Breyn., Auct. 



~N. TEXANUS? SHUM. 



PI. 9, Fig. 3, a, &. 

 (N. Texanus, Shumard. Trans. Acad. of Sciences St. Louis, 1860, p. 590.) 



SHELL subglobose. Whorls increasing rapidly in size. Body 

 whorl, sides convex, narrowing towards the dorsum, widest, about 

 a third of the distance from the ventral to the dorsal side ; back 

 rounded, sides sloping convexly and somewhat rapidly from the 

 widest part towards the umbilicus. Umbilicus small, apparently 

 not covered. Surface marked by a number of undulations, which 

 arise at or near the umbilicus, pass straight to the middle of the 

 whorl, whence they arch gracefully backwards, crossing the dor- 

 sum, where they are most strongly marked. Siphon nearly cen 

 tral, a little nearest the dorsal side. Septa gently undulated; 

 and, at their widest part, placed about one-fourth the width of 

 the whorl apart. 



Figures, two-thirds of the natural size. 



Three specimens were obtained at Alderson's Gulch, Shasta County ; and one 

 from near Mount Diablo, in Mr. Pioche's collection ; the last was found by Mr. 

 Clayton. (Div. A.) 



The specimens from which Dr. Shumard described his species were all imper 

 fect. I refer the present form provisionally to the Texas species, with which I 

 am unacquainted, since it seems to agree very closely with Dr. Shumard's descrip 

 tion. 



ATURIA, Bronn. 

 Megasiphonia, D'Orb. 

 A. MATHEWSONII, n. s. 



PI. 17, Fig. 31. 



SHELL subglobose, whorls increasing rapidly in size, deeply 

 enveloping; sides sloping regularly towards the dorsurn, some- 



