ASTEKOIDEA OF NORTH PACIFIC AND ADJACENT WATERS FISHER. 



157 



Hepatic coeca large, extending; halfwaj- to tip of ray. Each consists of a smooth- 

 walled ventral half, Uke a trough, the upper linlf being wider and divided with 

 dorso-ventrally plicate walls. Ventral stomach small with stout retractor muscles. 

 Gonads in a single thick tuft on either siile of the membranous interradial sejjtum. 

 Polian vesicles large; a[)parently one on each interradius. No supcrambulacral 

 plates. Ambulacral ossicles small and crowded. First pair greatly eidarged, each 

 with a higli rounded crest. Between these crests run transversely a thick muscle 

 band. The enlargement of the first pair of ambulacrals with the accorapanjnng 

 development of the dorsal transverse muscles is undoubtedly connected with the 

 movement of the combined mouth plates. These, being angular, almost completely 

 close the actinostome, and the small marginal spines completely close the opening. 

 Owing to the small size of tlie actinostome the stomach is ]>robably protruded, as 

 in Asterias, an assumption to whicli weight is given by the strong retractor muscles. 

 The enlargement of the first pair of ambulacrals is abrupt, and so noticeable as to 

 form a good generic character. The same enlargement occurs, but in a less degree, 

 in Asterodon singulai^is (Miiller and Troschel). Tube feet small, with sucking disks. 

 No deposits in walls. 



Variations. — Variation in this species is comparatively slight. The sides are 

 a trifle more arcute in some indiviiluals than in others. The number of marginal 

 plates varies, with size, from five to a ray (eleven to side of body) in a specimen 

 with R=7..5mm. to eight in the t_\'])ewith R = 21 mm. The granulation is a little 

 coarser on marginal plates in one or two specimens than in type, and the actinal 

 spinulation is longer and closer (stations 4.312, 2007). Small specimens have fewer 

 spinelets to actinal and abactinal plates and the papular areas are much smaller. 

 In the smallest specimen, mentioned above, there are about five adambulacral 

 spinelets, two of which stand on the f lu-row margin, the marginal plates are extremely 

 massive, and the largest radial paxillaj have ten to fifteen spinelets. 



Type.— C&t. No. 22333, U.S.N.M. 



Type-locality. — Albatross station 4313. vicinity of San Diego, 92 to 243 fathoms, 

 gra}' sand, broken shells. 



Distribution. — Monterey Bay to San Diego, CaUfornia, 43 to 284 fathoms. 



Specimens examined. — Eleven, from the following stations : 



Specimens of Odontaster crassus e-xamined. 



Locality. 



Depth. 



Nature ol bottom. 



45 



nO-143 

 135-95 

 92-243 

 118-53 

 74-05 



<xt-m 



43 



yellow mud 



fine gray sand 



coarse gray sand, broken shells, 



green mud, flncsand 



line greenish gray sand, rocks. . 



gray sand, shells, rocks 



rocky 



rocks 



green mud, rocks 



beach worn pebbles and stones, 

 broken shells. 



U. S. Nat. Mus. 



Albatro$i. 19M. 



University of California. 



