140 MESOZOIC AND CENOZOIC ECHINODERMATA OF THE UNITED STATES. 



Order ATELOSTOMATA. 



Suborder ASTEENATA. 



Family CASSIDULIDJE. 



Genus CASSIDUUJS Lamarck. 



Cassidulus californicus F. M. Anderson. 

 Plate LXV, figure 2a-b. 



Cassidulus californicus F. M. Anderson, 1905, California Acad. Sci. Proc, 3d ser., Geology, vol. 2, No.' 2, p. 194, PL 



XIII, figs. 6, 7. 

 Cassidulus californicus Arnold, 1909, U. S. Geol. Survey Bull. 396, p. 13, 112, PI. IV, figs. 1, la. 



Cassidulus californicus Arnold and R, Anderson, 1910, U. S. Geol. Survey Bull. 398, pp. 70, 284, PI. XXVI, figs. 1, la. 

 Cassidulus californicus Stefanini, 1911, Soc. geol. italiana Boll., vol. 30, p. 696. 



Description. — As the writer has not been able to obtain possession of any specimens of this 

 species the description of Anderson is given verbatim: 



Test small, elliptical, robust and often somewhat globular; lower surface flattened, or concave, upper surface convex; 

 mouth not central, round, and occupying a position three-fifths of the distance from the anal margin ; anal pore terminal; 

 apical star nearly symmetrical, central, on dorsal surface; tuberculation distinct, the tubercles lying within rounded 

 pits. There is a tendency to form shoulder-like expansions on the periphery behind the position of the mouth. 



Anderson does not mention a fioscelle nor do his figures show one, but the figured specimen 

 of Arnold shows a fioscelle distinctly. v Arnold's figures also show a test with a suboblong margi- 

 nal outline and a supramarginal periproct, apparently transverse, beneath an overhanging 

 expansion of the test. Arnold's form, here refigured, was 21 millimeters long. 



Locality. — Four Hides west-northwest of Coahnga, Cal. 



Geologic, horizon. — Tejon formation, upper Eocene. 



Collections. — California Academy of Natural Sciences; U. S. National Museum (165664). 



Cassidulus (Rhynchopygus ?) holmesi Twitchell, n. sp. 

 Plate LXV, figures 3a-d. 



Determinative characters. — Test small, broadly oval, slightly truncated at the posterior end; 

 upper surface convex, sides and ends rounded and inflated; under surface concave around the 

 peristome. Ambulacral areas narrow, petaloid; petals nearly equal, partly open. Apex cen- 

 tral; apical system excentric anteriorly. Peristome excentric anteriorly, pentagonal, longitu- 

 dinally elongate, with a fioscelle. Periproct elliptical, transverse, supramarginal; located in a 

 rather deep, oval indentation whose edges are almost flush with the posterior surface of the test. 



Dimensions. — Length 25 millimeters; width 22.5 millinieters; height 14 millimeters. 



Description. — Only a single specimen of this interesting species is known to the writer. It 

 was found in the F. S. Holmes collection, now owned by the American Museum of Natural 

 History, and as it was probably collected by Holmes is named in his honor. The test is small, 

 broadly oval, being but slightly longer than it is broad, slightly truncated at the posterior end. 

 The upper surface is regularly convex, somewhat elevated, sides and ends sloping nearly uni- 

 formly to the rounded and inflated margin; under surface tumid around the margin, concave 

 around the peristome; apex central. 



The ambulacral areas are rather narrow, dorsal portions petaloid; petals nearly equal in 

 length, the posterior pair being but slightly longer than the others, nearly closing at the ends. 

 The poriferous zones are rather broad, outer row of pores oval, inner row round, pairs of pores 

 conjugate. 



The surface of the test is closely set with small tubercles in deep scrobicules, which are 

 larger on the under surface except along a cribriform median band. 



The apical system is excentric anteriorly. There are four genital pores of which the ante- 

 rior pair are nearer together than the posterior. No further details can be made out on the single 

 specimen known. 



