North American index fossils, invertebrates . Fig. 1919. Leiocidaris hemigranosa, upper and lateral views, x %>(After Clark.) large, not crenulated. Spines large, smooth, cylindrical. Cretacic- Recent. 19. L. hemigranosa (Shumard). (Fig. 1919.) Comanchic. Ambulacral areas with six rows of granules in the middle. Pore-bearing zones deeply depressed. Denison (Washita) of Texas. Order DIADEMATOIDA Duncan. XII. Diadem A Schynvoet (includes Pseudodiadema Desor). Test highly ornamented. Ambulacra straight, with two verticalrows of small primary perforate and crenulate tubercles extendingfrom mout
North American index fossils, invertebrates . Fig. 1919. Leiocidaris hemigranosa, upper and lateral views, x %>(After Clark.) large, not crenulated. Spines large, smooth, cylindrical. Cretacic- Recent. 19. L. hemigranosa (Shumard). (Fig. 1919.) Comanchic. Ambulacral areas with six rows of granules in the middle. Pore-bearing zones deeply depressed. Denison (Washita) of Texas. Order DIADEMATOIDA Duncan. XII. Diadem A Schynvoet (includes Pseudodiadema Desor). Test highly ornamented. Ambulacra straight, with two verticalrows of small primary perforate and crenulate tubercles extendingfrom mouth to apex. Pairs of pores in simple vertical series or inarcs of threes. Interambulacra with two or more vertical rows of ECHINODERMATA—ECHINOIDEA. 587 primary tubercles resembling those of the ambulacra but larger. Secondary tubercles and granules surrounding the areolas. Spines long, hollow, longitudinally striated. Mouth large, polygonal. Jurassic-Recent. 20. D. (Pseudodiadema) texanum (Roemer). (Fig. 1920.) , depressed.
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