158 University of California Publications in Geology [Vol. ll 



SPISULA RAMONENSIS Packard 



Plate 9, figures 4 and 5 



Spisula ramonensis Packard, Clark, Univ. Calif. Publ., Bull. Dept. Geol., 



vol. 9, no. 2, p. 15, 1915. 

 Spisula albaria ramonensis Packard, Univ. Calif. Publ., Bull. Dept. Geol., 

 vol. 9, no. 15, p. 291, pi. 23, fig. 5; pi. 25, figs. 1-2, 1916. 

 Occurrence. — A very common species in the Agasoma gravidum beds, Univer- 

 sity of California localities 1131, 1309, etc. ; also common in the Oligocene of 

 Oregon and Washington. 



This is one of several species which are very close in outline and 

 sculpturing to 8. albaria Conrad. The exact horizon from which 

 Conrad's species came is not certain. W. H. Dall 129 has redescribed 

 the species, taking as a pleseotype a specimen from the Empire beds 

 of Coos Bay, Oregon, which horizon is, at least approximately, equiva- 

 lent to what is recognized as Middle Pliocene in California, the same 

 horizon as the Lower Merced and Lower Wildcat. Earl Packard, in 

 his paper on the Mactrinae of the West Coast, has accepted Dall's 

 determination. The writer feels that it is very possible that Dall's 

 determination of 8. albaria is incorrect. Conrad's type came from 

 near Astoria, Oregon. As far as known, Pliocene beds are not pres- 

 ent in that vicinity. Packard has shown that the form from the 

 Monterey of Contra Costa County, 8. selbyensis Packard, previously 

 listed as 8. albaria, is distinct, as well as the one from the Agasoma 

 gravidum beds, 8. ramonensis, though he lias listed the latter as a 

 variety of S. albaria. It remains to be proven whether the Pliocene 

 species extends down into the Lower Miocene. It is very improbable 

 that it extends into the Oligocene. Both 8. ramonensis and 8. selby- 

 ensis Packard are very similar in outline and sculpturing to 8. albaria 

 Conrad, the form recognized by Dall and so common in the Upper 

 Miocene and Pliocene of the West Coast. The range of variation in 

 outline of all three species is so great that many times it is difficult 

 to separate them unless the hinge plates are exposed. Packard has 

 shown that the three species, as shown by the hinge plates, are quite 

 distinct and that one with good material can also see slight differences 

 externally. 



SPISULA RAMONENSIS ATTENUATA, n. var. 

 Plate 9, figure 6 

 Type specimen 11119, Coll. Invert. Palae. Univ. Calif., loc. 1167 

 Shell medium in size, longer than high, equivalved, inequilateral ; beaks fairly 

 conspicuous, strongly inturned, anterior to middle. Anterior dorsal slope long 



129 U. S. Geol. Surv., Prof, paper no. 59, pp. 130-131, pi. 10, fig. 1, 1909. 



