ASTEROIDEA OF NORTH PACIFIC AND ADJACENT WATERS FISHER. 85 



tlie surface is covered with a few spaced spinules one or two of which may be enlarged. 

 This pecuHarit}' of tlic true furrow spinclets is repeated in the furrow series of the 

 mouth plates. In penicillatus the furrow spines of mouth plates are also situated 

 high on the side of plate, which thus maintains an arrangement lost (or never 

 acquired) by the adambulaoral plates. 



Genus DIPSACASTER Alcock. 



DipsacastcT Alcock, Ann. and Mag. Nat. Hist., ser. 6, vol. 11, 1893, p. 87; Journ. Aeiatic Soc. 

 Bengal, vol. 62, 1893, p. 172 (no diagnosi.s). Type, D. sladeni Alcock. 



Diagnosis. — Rays five. General form depressed with broad disk and well- 

 developed actinal interradial areas; abactina! surface flat, not arched; marginal 

 plates large, the inferoniarginals always broader than superomarginals and typically 

 extending laterally beyond them and forming a subserrate l)order to ray; fasciolar 

 channels deep and conspicuous, tlie ridges being correspondingly highly developed; 

 inferomarginals with a tuft of spines at outer end, or these may be exceptionally 

 absent, the superomarginals sometimes ■with one to three small tubercles; covering 

 of plates ranging from capillary spinelets to poh'gonal granules; paxilla liiglJy 

 characteristic, composed of a tall pedicel springing from a round or stellate base and 

 crowned with a glomerular tuft of very many slender crowded spinelets; papulae 

 typically distributed all over the abactinal surface, in sixes or fives about the plates ; no 

 internal independent ossicles connecting plates; actinal intermediate plates carinated 

 and imbricated, bearing a paxilliform group of spinelets, there being fasciolar chan- 

 nels leading from inferomarginals to adambulacrals; adambulacrals not compressed, 

 with a palmate or pectinate furrow series of cjdindrical or much compressed spines, 

 and a variable number of smaller spinelets on exposed surface of plate, the latter 

 usually not regularly arranged; mouth plates prominent actinally, rather broad, 

 \vith numerous spinules on exposed surface, and a marginal series resembling those 

 of adambulacrals; madreporic body typicallj- very large, hidden by many large 

 paxillae springing from its surface. Anus always present, connected with an 

 unbranched sac-like intestinal ccecum, Ijing in the left radius of trivium (or adjacent 

 interradius of biviuni), the latter connected with stomach by a short intestine; 

 superambulacral plates always present; tube feet pointed, without calcareous 

 deposits; gonads extending far along my, the genital tubules depending from a 

 genital stolon and decreasing in size distad. 



KEY TO THE SPECIES OF DIPS.<.CASTER HEREIN DESCRIBED. 



a'. Inferoraarginal plates with a tuft of enlarged spines at outer end or a series along aboral margin; 



border of rays subserrate; papulae distributed all over abactinal surface; madreporic plate very 



large bearing many paxillae on its surface. 



b'. Paxilla; conspicuously larger in central portion of disk and along median area of rays, their spinelets 



descending the pedicel in bristling array, so that they resemble minute bottle-brushes; rays broad 



near tips; abactinal plates strongly stellate along median radial area, with two or three papulae 



to each area instead of one; actinal intermediate areaa broad, far along ray erimius, p. 86. 



6^. Paxillse not conspicuously larger in central portion of disk, etc., their spinelets grouped at top of 

 pedicel; rays evenly tapered to tip; abactinal plates along median radial area either round or 

 stellate, but not surrounded by many papulae, never by more than eight; actinal intermediate 

 areas narrow beyond middle of ray. 



