184 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



The large specimen from station 5630, it will be noted, has pedicel- 

 lariae only on the actinal interradial areas. It is of a stouter build 

 than the other specimens, the marginal spines being very robust. 

 This, and to a less extent the specimen from station 5660 (also 

 from a lesser depth than the majority oi examples), resemble the 

 form called '"'' Pontaster forcipatus^ var. ecJiinata^'' by Sladen. The 

 stouter habit may be correlated with the difference in depth. 

 Koehler also notes a similarity to ecMnatus in some of his speci- 

 mens of hispidud (1909, p. 12). It would be interesting to know if 

 these specimens are likewise from shallower water (stations 250 and 

 317, 480 and 590 fathoms). 



The number of adambulacrals to the first 10 inferomarginals 

 varies in full-sized specimens from 15 to 18, but 15, 16^. or 17 is the 

 usual number. 



The abactinal paxillae conform to the figures and descriptions of 

 Sladen, except that in specimens from stations 5609 and 5668 a few 

 abactinal pedicellariae are present. These are found on the disk or 

 base of rays and have 2 to 4 short jaws, thicker than the paxillar spine- 

 lets. Beyond the interbrachial arc the marginal plates have a 

 considerable area around the spines in which the spinelets are 

 irregularly and widely scattered. There are sometimes 2 accessory 

 inferomarginal spines at the base of the ray. The inferomarginal 

 pedicellariae, usually 1 but occasionally 2 to a plate, are subcir- 

 cular and occur on the suture betw^een the inferomarginal and adam- 

 bulacral plates (with most of the spinelets on the former) or on 

 the inferomarginal close to the lower edge. There are usually 4 to 

 C stout, tapering, pointed jaws, much stouter than the neighboring 

 spinelets. The actinal interradial pedicellariae stand on 1 or 2 

 plates, and when well developed have 7 or 8 jaws. They are usually 

 subcircular, but sometimes assume a double-pectinate form, more 

 as in Cheiraster, but retain the stout jaws. In Cheiraster the jaws 

 of the pedicellariae are relatively slenderer. 



On the outer part of the ray (sometimes for as much as the distal 

 half) the adambulacral plates have a second smaller upright spine, 

 situated between the principal subambulacral spine and the furrow 

 margin. It occasionally nearly equals the principal spine in size, and 

 seems to be, morphologically, an aboral furrow spine which has 

 nuoved onto the surface of the plate. This spine is not mentioned by 

 Sladen, but it might be easily overlooked. 



The dorsal muscle bands are each attached to the outer end of 

 fifth ambulacral plate (specimens from stations 5609, 5668) by a 

 slender rather inconspicuous tendon, once to twice as long as the 

 transverse dimension of the ambulacral plate. A second very incon- 

 spicuous tendon can be traced to the seventh plate, or to one of a 

 few succeeding plates. The fifth ambulacral is higher than the 



