224 BULLETIN 76, UNITED STATES NATIONAL MUSEUM. 



one to six tubercular spines, a periplieral series of granules, and occasionally bivalved 

 petlicellarifc; general surface of marginals not covered with granules. Actinal inter- 

 mediate plates armed with pedicellariae and various-sized granules and tubercles. 

 Tho body surface is covered by a skin which, however, usually does not obscure the 

 plates or granules, and is typically only evident by the thin covering of the granules 

 and by wrinkles between the plates; exceptionally it is thick enough to obscure 

 the borders of the plates, which with the granules then appear immersed. Tube 

 feet with heavy sucking disks. No superambulacral plates. 



KEY TO THE SPECIES OP HIPPASTERIA HEREIN DESCRIBED. 



a'. Marginal plates well developed, eubquadrate, not separated by encroaching abactinal or actinal 

 intermediate plates; granules fairly or quite smooth, 

 fc'. With conspicuous abactinal spines and abactinal surface of marginals not smooth and unarmed. 

 c'. Pedicellarise shorter and higher; dorsal surface very spiny; as a rule no pedicellaria; on mar- 

 ginal plates; actinal pedicellarise with oblong or eubquadrate jaws; actinal intermediate 

 plates not conspicuously tuberculate; abactinal granules in definite marginal series about the 



plates, abactinal skeleton not fenestrated spinosa, p. 224. 



c^. Pedicellarise low, long; a well developed pedicellaria on the proximal superomarginals, and 

 on most of the inferomarginal plates; papulae conspicuous, bag-like; actinal intermediate 

 plates tuberculate; actinal pedicellariae very low, long; abactinal granules small conical, 

 scattered, abactinal membrane thick; abactinal skeleton when viewed from inner side honey- 

 combed or fenestrated heathi, p. 231. 



6^. No abactinal spines or tubercles (or only exceptionally and abnormally present, and then very 

 few); abactinal plates mostly smooth, bordered by a single row of stout granules; marginals with 

 all except lateral surface bare; lateral spines small and unequal, one or two to a plate or absent; 



adambulacral spines two, clavate, in a transverse series leiopelta, p. 227. 



a'. Marginal plates weak, irregular, oval, or elliptical, the proximal usually separated by encroaching 

 plates from the dorsal and ventral surfaces; actinal pedicellariae high, rather delicate, flaring at 

 base, and with narrow curved serrate tips; granules rugose or denticulate calif arnica, p. 233. 



HIPPASTERIA SPINOSA Verrm. 



PI. 42, figs. 1-3; pi. 43, figs. 1, 2; pi. 60, fig. 4. 



Bippasteria spinosa Verrill, Amer. Journ. Sci., vol. 28, July, 1909, p. G3. 



Diagnosis. — Similar to IJ. plirygiana of the north Atlantic, but primary abac- 

 tinal and marginal plates with prominent, often long, tapering blunt spines rather 

 than the elongate tubercles of pJirygiana. 



Description. — Rays five. R = 11 mm. ; r = 56 mm. ; R = 2 r. Breadth of ray at 

 base, 64 mm. General form same as pJu^giana, but rays a trifle broader. Majority of 

 the larger or primary abactinal plates convex and bearing in center a stout, upright, 

 rigid, tapering truncate spine, one to two times width of its plate in length; mid- 

 radial spines slightly the longest, thence decreasing in length to margin of area; 

 same plates in phnjgiana bearing a very much shorter, stouter tubercle, truncate 

 or rounded at apex. General surface of plates smooth, but rim encircled by a 

 single series of irregular, small, subcorneal or roundish granules heavily invested with 

 membrane. Many large and smaller plates bear a large central bivalved pedicel- 

 laria, the jaws of which are only slightly wider than high; sometimes the two 

 dimensions are equal. These pedicellarise are usually narrower and higher than 

 those of plirygiana and have thinner blades. Distal edge of jaws is slightly curved, 

 either serrate or smooth. Small intermediate plates intercalated between the 



