CRETACEOUS FOSSILS. 59 



NAUTILUS, Breyn., Auct. 



K Texanus? Shum. 



PI. 9, Pig. 3, a, b. 

 {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 ; hack 

 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. 



Pigures, two-thirds of the natural size, 



Three specimens were ohtained at Anderson'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, Pig. 31. 



Shell subglobose, whorls increasing rapidly in size, deeply 

 enveloping ; sides sloping regularly towards the dorsum, some- 



