KEPOKT ON THE ASTEROIDEA. 93 



protrudes over the actinostome, which is contracted and nearly closed. Their armature 

 consists of a marginal series of about nine short papilliform spinelets on each plate, 

 nearly subequal in length, the outermost being slightly smaller, standing upright and 

 parallel to one another. The actinal surface of the plate is covered with numerous rather 

 broad granuliform papillae, truly granules on the outer portion of the plates, but becoming 

 loDger and more papilliform as they approach the inner end of the mouth-antde, the 

 innermost three or four being nearly as long as, and more robust than, the marginal series. 

 All are very obtusely tipped. 



The actinal interradial areas are large and well-developed, extending as far as the twelfth 

 or thirteenth adambulacral plate. They are occupied by well-defined plates arranged in 

 regular series or columns extending from the adambulacral plates to the infero-marginal 

 plates. The innermost plate of each series is normally subequal in breadth to the adjacent 

 adambulacral plate, and the columns diminish in breadth as they proceed towards the 

 margin. Seven plates may be counted in the series on each side of the median interradial 

 line. The surface of the plates is covered with closely placed hemispherical granules of 

 simdar size and character to those on the adambulacral and marginal plates, disposed in 

 regular subrectangular groups, each group being marked out by distinct and well-defined 

 sutures or channels from those adjacent. The regularity of the arrangement is constant 

 and very conspicuous. 



The anal aperture is subcentral, and, though comparatively large, is inconspicuous, as 

 there is no modification in the character of the surrounding paxillse. 



The madreporiform body is entirely obscured by paxdlas, a group of five or six in this 

 region being larger and slightly more prominent than any of the others. These indicate 

 its position, which is rather nearer the margin than midway between the centre and the 

 interbrachial arc. It is possible that the madreporiform body may be of large size or even 

 compound, judging from appearances ; but these remarks are purely conjectural, as the 

 fact cannot be decided without damaging the specimen. 



The ambulacral tube-feet are large and conical, with a very small, mamelon-like, conical 

 termination. 



Colour in alcohol, a very light drab, with an ashy grey shade of the same on the 

 paxillar area. 



Locality. — Station 44 or 45. Off the coast of North America, east of Delaware and 

 Maryland. 



Station 44. May 2, 1873. Lat. 37° 25' 0" N., long. 71° 40' 0" W. Depth 1700 

 fathoms. Blue mud. Bottom temperature 36° - 2 Fahr. ; surface temperature 56° - 5 Fahr. 



Station 45. May 3, 1873. Bat. 38° 34' 0" N., long. 72° 10' 0" W. Depth 1240 

 fathoms. Blue mud. Bottom temperature 37° - 2 Fahr. ; surface temperature 49°*5 Fahr. 



Remarks. — Plutonaster rigidus is distinguished from Plutonaster ambiguus by its 

 larger size, by the large marginal plates, by the absence of a prominent tubercle on the 



