301 



Rays short , robust , swollen , evenly tapered or slightly inflated at 

 middle; extremity bluntly pointed; disk capable of considerable inflation ; 

 whole animal appearing inflated and turgid; integument fairly thick; 

 abactinal and lateral surfaces marked off into large areas by narrow, 

 rounded, raised ridges — the skeleton — bearing, usually at corners of 

 areas, prominent, widely spaced, isolated, conical, pointed spines, irre- 

 gularly arranged in a median radial, 1 to 3 dorso-lateral (in young 

 specimens often no dorso-lateralsj , a superomarginal, 1 or 2 incomplete 

 intermarginal series (of much shorter spinules), and an inferomarginal 

 series; actinal intermediate areas fairly prominent, usually with 1 or 2 

 irregular series of spines extending partway along ray. Papular spaces, 

 between trabeculae of skeleton, are sub(|uadrate or irregular, containing, 

 on disk, about 50 fairly conspicuous papulae, these decreasing gradually 

 to 15 or 30 beyond middle of ray; intermarginal papular areas with 

 about 25 papulae; no actinal papulae. The lobed primary plates of the 

 skeleton are connected by intermediate oblong- elliptical, overlapping 

 ossicles forming the trabeculae, and on disk the ridges form an irregular 

 pentagon (corners radial) within which is a second, more regular and 

 stellate pentagon, the corners (interradial) touching sides of larger 

 pentagon. Fine creases or lines in the integument proceed outward, 

 between the spines, from the adambulacral to marginal plates. 



Preparation of body -wall shows that the papular areas contain 

 many small scattered calcareous grains, most numerous near central 

 portion of each area. 



Adambulacral plates considerably wider than long. Armature 

 consists of (1) a single truncate, or round-tipped furrow spine, 3,5 mm 

 long, compressed and usually strongly grooved along upper (or outer) 

 side; (2) on actinal surface a similar but slightly longer upright spine, 

 usually very conspicuously gouge-shaped at tip. Spines and surface of 

 plates are covered with membrane. 



Madreporic body is situated at about middle of minor radius; 

 striations, irregularly centrifugal. 



Color in life: general tint cream color, abactinal surface lighter; 

 apical area huffy yellow. 



Habitat. Monterey Bay, about 140 metres. 



Remarks. This species evidently belongs to Lud wig's recently 

 described Alexandraster (Mem. Mus. Comp. Zool. XXXII. 1905. 210). 

 The type species was taken in the Gulf of Panama (837 m), and near the 

 Galapagos Islands (702 m). Inflatus differs from mirus^ to which it is 

 closely related in having shorter and thicker rays , and in possessing 

 strongly grooved adambulacral spines. The furrow spines are pro- 

 minent and not conspicuously smaller than those of actinal surface — 



20* 



