Clark: The San Lorenzo Series of Middle California 191 



Dentalium substriatum Conrad, Gabb, Geol. Surv. Calif., Palaeontology, 



vol. 2, p. 115, 1868. 

 Dentalium conradi Dall, n. nom., U. S. Geol. Surv., Prof, paper no. 59, 



p. 136, 1909. 



Dentalium conradi Dall, Arnold and Hannibal, Proc. Amer. Philos. Soc, 



vol. 52, no. 212, pp. 581, 583, 584, 588, 1913. 

 DentaUum conradi Dall, Weaver, Univ. Wash. Pnbl. Geol., vol. 1, no. 1, 



p. 30, 1916; Calif. Acad. Sei., ser. 4, vol. 6, no. 2, p. 37; also no. 3, 



p. 51, 1916. 



Dentalium conradi is a common species in both the Oligocene and 

 Lower Miocene of the West Coast. 



DENTALIUM EADIOLINEATA, n. sp. 

 Plate 22, figure 12 



Type specimen 11227, Coll. Invert, Palae. Univ. Calif., loc. 1131. 



Shell medium in size, gently curved, cross-section circular ; apex slender, not 

 notched. Surface covered by about sixteen fairly heavy, radiating ribs with 

 interspaces considerably wider than the ribs. On the smaller specimens the radiat- 

 ing ribs cover the entire shell ; on large specimens, however, they become faint 

 or obsolete near anterior end. 



Occurrence. — University of California localities 1131, 1173, 1631. 



DENTALIUM EADIOLINEATA SOBBANTENSIS, n. var. 



Plate 14, figures 9 and 10 



Type specimen 11261, Coll. Invert, Palae. Univ. Calif., loc. 1173 

 Dentalium cf. stramineum Gabb, Clark, Univ. Calif. Publ., Bull. Dept. 

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

 Occurrence. — University of California locality 1173. 



A couple of specimens were found at University of California 

 locality 1173, which the writer in a previous paper referred to D. cf. 

 stramineum. Further study shows that this should probably be con- 

 sidered a variety of D. radiolineatum, n. sp., from which it differs in 

 the presence of a less prominent interrib between the longitudinal 

 ribs ; also, the surface, on the more unweathered portions of the shell, 

 is covered with very fine longitudinal striatums, which are on both 

 the ribs and the interspaces. This last character is observable only 

 on exceptionally unweathered specimens and it may A^ery possibly 

 be found to be a characteristic of the typical D. radiolineatum. 



Class AMPHINEURA 



Plate 14, figure 2 



An anterior plate of a chiton was found at University of California 

 locality 1131. The form has not been determined either generically 

 or specifically. 



