TERTIARY FOSSILS. 47 



SURCULA, H. & A. Ad. 



S. Tryoniana, G. 



(Pleurotoma (Surcula) Tryoniana, G., Pal. Cal., V. 2, p. 6, pi. 1, fig. 9.) 



This very rare shell is known by but two specimens. One is that figured as 

 above, from the Post-Pliocene of San Pedro ; the other is a dead and very much 

 decayed shell, picked up by me on the beach near San Pedro, but undoubtedly 

 recent. 



NASSA, Lam. 



S. G. CiESiA, H. & A. Adams, 1857. 



Schizopyga, Con., 1857. 



In " Genera of Recent Mollusca," H. and A. Adams describe a large number 

 of subgenera of Nassa, among which is the present one. The description reads, 

 "Spire elevated, whorl rugose or cancellated, rounded; inner lip with the callus 

 defined; outer lip thin, simple." This description covers all of the subgeneric 

 characters which belong to either Nassa perpinguis, Hinds, or Buccinum fossatum, 

 Gld. The former species was placed by them correctly, under this head ; while 

 the latter, a closely allied species, and one which, in some of its varieties, is diffi- 

 cult to distinguish from some of the varieties of perpinguis, is placed by them 

 under the subgenus Tritia. To add to the confusion, N. Cooperii, Fbs., is also 

 included in Tritia, while mendica, Gld., is called a Niot/ia. The last two species 

 belong, without question, to the same group, and are so nearly related that their 

 specific difference has been denied more than once, by excellent authorities. With 

 this portion of the question, however, we have nothing to do at present. 



The Adams's have defined clearly all of the important characters of the group 

 to which they have given the name ; unless we add that, in both the species in 

 question, the callus on the inner lip is transversely wrinkled. The same year, in 

 Vol. 6, Pacific Railroad Reports, Mr. Conrad described a genus, of which he said, 

 " the above genus is probably related to Cancellaria," and which he defined as fol- 

 lows: " Bucciniform ; columella concave, plicate; lower part of body volution 

 deeply channelled, the channel emarginating the columella." 



It will be seen that the description is based principally on the deep depression 

 formed by the twisting of the anterior part of the shell, a character of common 

 occurrence in a majority of the Nassas, and visible to a greater or less extent in 



