124 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



In S. oregotiensis the ventral lobe has only slight subdivisions or none; the 

 lateral saddles are simple and rounded, the smaller divisions amounting to 

 only shallow scallops. The lateral lobe also shows a corresponding sim- 

 plicity of detail. This contrasts considerably with the more deeply cut lobes 

 and saddles of S. propinqua. 



In S. propinqua the ventral lobe is divided by a siphonal indentation of 

 noticeable depth. 



Both of these species appear to belong to Neumayer's 

 genus Schloeiibachiu, which probably includes the following 

 species. 



71. Schloenbachia blanfordiana Stol. (?) 

 Plate I, Figs. 5-10. 

 Ammomies blanfordianus Stol., Pal. Ind., Vol. I, p. 46, PI. XXVI. 



Among the collections made at the Forty-nine Mine, in 

 Southern Oregon, are several specimens of a shell plainly 

 of the type of Stoliczka's species, and at least very closely 

 related to it, if not identical. 



The shell is fiat and discoidal, with moderately wide umbilicus surrounded 

 by about fourteen or more elevated tubercules; sides ornamented with about 

 forty ribs, which are clearly distinguishable on shells below a diameter of 

 3 cm., but becoming obsolete with age. The sides of the older whorls are 

 smooth, with the exception of the tubercules bordering the umbilicus and 

 the ventral margin. The ribs when they appear are flexuous, and show on 

 one specimen a tendency to form nodes considerably below the umbilical 

 row. The shell becomes a little more involute with age and finally clasps 

 about one-half of the preceding whorl. The keel is never prominent and 

 with increasing growth becomes, at a diameter of 3 cm., undulating and 

 apparently obtuse at 4.5 cm., or reduced to an obtuse ventral angle. The 

 suture, as far as it can be seen, agrees reasonably well with that of Sto- 

 liczka's figure, showing the same general character of lobes and saddles. 



The ribs of the Oregon species seem to become lost at an earlier age than 

 in the Indian form, and the number of umbilical tubercules is not so great. 

 On the 3'oung shells the ribs first make their appearance at a diameter of 

 I cm., beginning at the ventral margin in small tubercules. 



Occurrence. — This shell was found at the Forty-nine 

 Mine, near Phoenix, Oregon. It belongs to a horizon 

 equivalent to that of the Lower Chico beds of California. 



