PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 13 



This, it will be observed, contains one hundred and seven well deter- 

 mined species, omitting several doubtful ones, of which ten are extinct 

 and ninety-seven still found recent. Of these recent or still existing 

 forms, twenty are found in the Californian fauna and northward at the 

 present time. Eighteen more are found in the Californian fauna and 

 southward, while forty-four are strictly Californian. Besides these, there 

 are eight species belonging to the Oregonian or Arctic fauna, and no 

 longer found living in the Californian region. Seven more are found 

 on the west coast of Mexico, the Gulf of California, or Western Middle 

 America, and, so far as known, no longer in the Californian region. 

 One or two species are still found living in Atlantic seas, but not on the 

 western shores of America. How far these peculiarities of distribu- 

 tion may be explained by a restriction of their geographical range in 

 modern times by some species, or by the association of fossils in one 

 collection from beds of differing age, and consequeutly exhibiting the 

 fluctuation of the northern and southern faunae based on varying 

 temperatures of the sea, will be determined only by a most critical 

 stratigraphical study of the localities. 



But in either case the problem is well worthy of solution. The very 

 modern character of the beds is determined by the great majority of 

 the species being still found living, and by the fact that some of them 

 retain very evident traces of their original coloration. They are mostly 

 in excellent preservation. The well fossils taken with those mentioned 

 on p. 3 would give a vertical range of some six hundred feet for the 

 Pliocene Tertiary beds of California. 



The species which appear to be new are as follows: — 



Axinea profunda, n. s. (7935). 



Shell subtriangular, ventral margin rounded, umbos erect, rather 

 small. Area narrow, deep; marked by five or six lines meeting at an 

 angle in the vertical of the umbo, one above another; anterior lines 

 somewhat the shortest; exterior marked by twenty-five or thirty flat- 

 tened ribs, separated by deep channels one-fourth as wide as the ribs, 

 and by which the interior margin is crenulated. The ribs are crossed 

 by thread-like close lines of growth, which may be elevated or obsolete 

 on the ribs, but are sharply defined in the channels, which they partially 

 fill up in some specimens. Toward the anterior and posterior margins? 

 the sculpture is nearly obsolete. In eroded examples, this sculpture 

 may be entirely altered, and such are hardly recognizable as the same 

 thing. Interior smooth or lightly radiately striate, with a tendency to 

 an elevated narrow ridge behind the anterior scar; hinge with teeth 

 placed as if radiating from the centre of the valve, six to nine anteri- 

 orly, and ten to fourteen posteriorly, with some ten or twelve small, 

 crowded teeth between the two radiating sets, and placed perpendicu- 

 larly and parallel with one another. Height, 32 mm ; length, oi) mw ; thick- 

 ness, 20 mui ; the last proportionally greater in the young. 



