150 University of California Publications in Geology [Vol.12 



Odd anterior petal slightly longer than the others. All petals in deep 

 sulci, the odd anterior one continuing beyond the petal through a 

 notch in the margin to the peristome on the under side. Peristome 

 situated well forward on the lower surface ; large, semilunar in shape, 

 and with prominent projecting labrum. Lower surface very slightly 

 convex and with weakly developed episternum. Periproct small, 

 round, and situated high up on the posterior truncation of the test. 

 Tubercles on upper surface small and numerous ; those on the under 

 side somewliat larger and not so crowded ; those on the actinal plastron 

 considerably larger than the others ; all with definite scrobicules. 



Related forms. — This species differs from Schizaster eliabloensis 

 Kew in having a more strongly depressed test, longer and narrower 

 posterior petals, and usually a more nearly cordiform outline. From 

 8. lecontei Merriam and S. niartinezensis Kew it is easily distinguished 

 by its less elongate and more depressed test. 



Geologic horizon. — Lower part of the Martinez group. Lower 

 Eocene. 



Locality. — Univ. Calif, loc. 1743, north side of Mount Diablo. 



SCHIZASTEE DIABLOENSIS Kew, n. sp. 

 Plate 41, figures 5a, 5b, 5c 



Schizaster lecontei. Dickerson, Uuiv. Calif. Pulil. Bull. Dept. Geol., vol. 8, 

 1914, pp. 121-122, pi. 6, fig. 7. 



HolotyiH'.—No. 11387 Univ. Calif. Coll. Invert. Pal. 



Test of medium size. Measurements of specimen 11387 : antero- 

 posterior diameter 24.2 mm., transverse diameter 26.7 mm., greatest 

 height 20.2 mm. Outline from above subcircular to slightly cordiform, 

 the transverse diameter often being greater than the anteroposterior 

 diameter. Posterior end very slightly truncated, if at all. Apical 

 system very small and somewhat sunken ; posteriorly eccentric. Sum- 

 mit behind the apical system on a low ridge which extends from the 

 apical system to the periproct. Upper surface slopes gradually from 

 the apex to the anterior part of the ambitus, but steeply to the pos- 

 terior part. Sides of test broadly rounded except in the posterior 

 portion, where they are nearly vertical. Ambulacra petaloid. Petals 

 of the bivium very short and subelliptical in outline ; anterolateral 

 petals broad and nearly three times the length of the posterior pair. 

 Inner rows of pores of paired petals diverge slightly at first and then 

 continue in nearly parallel lines to the end, whereas the outer rows 



