138 THE VOYAGE OF H.M.S. CHALLENGER. ■ 



one small conical spinelet at the junction of the pair of plates and two others on the 

 margin of each plate. The odontophore is visible. The actinal interradial areas are 

 covered with a complete pavement of plates. - 



Localities. — Station 45. Off the coast of North America, east of Delaware and 

 Maryland. May 3, 1873. Lat. 38° 34' 0" N., long. 72° 10' 0" W. Depth 1240 fathoms. 

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



Station 46. Off the coast of North America, east of New Jersey. May 6, 1873. 

 Lat. 40° 17' 0" N, long. 66° 48' 0" W. Depth 1350 fathoms. Blue mud. Bottom 

 temperature 37 c, 2 Fahr. ; surface temperature 40°'0 Fahr. 



Station 47. Off the coast of North America, east of New Jersey and Long Island. 

 May 7, 1873. Lat. 41° 14' 0" N, long. 65° 45' 0" W. Depth 1340 fathoms. Blue 

 mud. Surface temperature 42°'0 Fahr. 



Remarks. — This species is at once distinguished from the other members of the genus 

 by the single cribriform organ in each interbrachial arc, by the absence of segmental 

 pits and papillae, by the short rays, and by the spinelets on the abactinal membrane 

 being confined to limited areas which occupy the interradial lines and the central region 

 of the disk. 



2. Porcellanaster caulifer, Sladen (PI. XXI. figs. 5-10; PI. XXVII. figs. 9-12). 



Porcellanaster caulifer, Sladen, 1883, Journ, Linn. Soc. Lond. (ZooL), voL xvii. p. 222. j 



Pays five. R= 21 mm. ; r = 6-5 mm. E<3r. 



Rays moderately long and slender, not much broader at the base than at mid-arm, 

 tapering only slightly, the minor radius in the proportion of 30 per cent. Interbrachial 

 arcs rather flatly rounded. Disk high and much inflated. 



The abactinal area is covered with an integument, beset with spinelets, excepting at 

 the very base of the rays. The spinelets are simple, delicate, clavate, or thickened at 

 the extremity, covered with membrane, and rather widely spaced. Large papulse-like 

 bodies are distributed here and there. A very long tubular epiproctal prolongation or 

 anal funnel rises from the central region of the disk, in length nearly equal to the 

 minor radius, rather narrow and tapering towards the extremity. 



The marginal plates are moderately high, and form a perpendicular wall in the 

 interbrachial arc, but arch over on the abactinal surface of the rays, and leave only a 

 narrow space along the median line between the corresponding plates of the two sides. 

 The supero-marginal plates are seven in number, exclusive of the terminal ; all are longer 

 than high, and each carries a long, delicate, acicular spinelet. The terminal plate is 

 large and elongate, very slightly prominent abactinally, and flattened ; it normally 

 carries three spinelets, though sometimes more are present. These are longer than 

 the spinelets on the other supero-marginal plates, and are delicate and acicular ; one 



