230 BULLETIN 76, UNITED STATES NATIONAL MUSEUM. 



sliort, thick, and blunt to long and slender. They appear to be always shorter than 

 tlie correspondmg adambulacral spines. 



Actinal intermediate plates few and confined to the disk. Each bears a number 

 of small spaced si)inolets and usually one or two upright slender tapering spines, 

 similar to but smaller than those of adambulacrals. In each interradius there are 

 one to three (usually one or two) large circular pectinate pedicellarise composed of 

 two opposite series of eight to twelve convergent strongly incurved papilliform 

 spinelets. Rarely there are three groups, in whicli case there are fewer spinelets to 

 each. The plates bearing the pedicellarian combs usually have also one or two 

 ordinary spines, and numerous jiaiiilliform or granuliform spinelets. 



Madrcporic body convex, with very irregular strife. It is situated nearer margin 

 than center of minor radius. 



Color in life: some fresh alcoholic specimens from station 4791 showed unfaded 

 patches of bright vermilion, where alcohol had not had free access to the surface. 

 The tube feet seemed to be brightly colored also. 



Anatomical notes. — No superambulacral plates. Tube feet in two rows; sucking 

 disks well developed; ampullas double; one Polian vesicle in each interradius except 

 that of madreporic canal. Interbrachial septa membranous. Gonads confined to 

 interradial region and opening near marginal plates. Anus present. Intestinal 

 coecum large, with four thick lobes. Passage from coecum into dorsal stomach short 

 and narrow. Stomach not clearl}- divided into dorsal and ventral portions. Retract- 

 ors of stomach well developed ; coeca extending only a short distance into arm. No 

 calcareous particles in tube feet or walls of stomach. 



The two muscle bands on the ccelomic surface of the dorsal integument are 

 remarkably well developed. The tendon is attached to a special crest of the seventh 

 and eighth ambulacral ossicles, and also to the inner surface of the adjacent (third) 

 superomarginal. The tendon is about 9 mm. long, and the heavy muscle band which 

 immediately becomes attached to the dorsal integument tends slightly inward, 

 broadens a little and at about one-third R, joins the muscle of the other side. The 

 two run parallel, and closely joined to tip of ray, occupying the width of the narrow 

 paxillar area. Professor Ludwig has kindly sent me preparations of L. Mrsutus, 

 which show that the muscles are similarly attached in that species. This character 

 is useful, for some species of Luidiaster are superficially like Cheiraster. 



Variations. — The chief variations have been considered in the foregoing descrip- 

 tion. These concern the relative length and number of dorsal spines and their 

 accompanying spinules, the superomarginal and adambulacral spines, and the pedi- 

 cellarifc. Both actinal intermediate and abactinal pedicellarise are alwa3's present, 

 but variable in number. Some specimens have more numerous auxiliary spinules 

 surrounding the dorsal spines than others, and the accompanying miliary spinelets 

 are subject to considerable variation in length and number. The armature of the 

 marginal plates is essentially of the same character as that of the large paxillse or 

 dorsal plates. Large specimens from station 3320 and station 3223 have broader 

 rays than examples from deeper water, as for instance, station 3339. This variation 

 is probably not correlated with depth, as examples from station 4792 have rather 

 narrow rays. 



