ON TWO NEW SPECIES OF ASTHENOSOMA. 



9 



there are about 36 plates abactinally and about 26 plates actinally. The 

 number of ambulacral plates almost twice that of interambulacrals. 



Apical system (fig 1 1) polygonal, projecting. Anus very prominent. 

 Anal plates (an.) minute, of an elongated shape, few, not reaching anal 

 margin. Periproctal plates (per.) with pedicellariae and small spines. 

 Basal plates (bas.) unclosed, leaving around the genital opening (g.o.) a 

 narrow membranous tract (bas'.), containing numerous small calcareous 

 pieces and networks and extending as far down as the 8th. — 10th. 

 plates along the median interambulacral line. Madreporic plate divided 

 into 4 separate pieces of unequal size (mad.), the largest occupying the 

 normal position. This division of madreporic plate is probably merely 

 an individual abnormality. 



Ambulacrum straight, 20 mm. wide at ambitus. The arrangement 

 of ambulacral plates both coronal and peristomal, as also that of the 

 pairs of pores, essentially same as in the foregoing spscies. 



Tentacles of abactinal side pointed, containing exceedingly minute 

 calcareous pieces in a small quantity. In the proximity of ambitus, 

 first the inner tentacles and soon also the outer tentacles begin to be 

 provided with calcareous discs, as are all on actinal side except those on 

 peristome. The latter are simply provided with calcareous network. 



Tubercles of both ambulacral and interambulacral areas show 

 marked difference on actinal and abactinal sides. 



Primary tubercles of interambulacrum : these appear from the 

 23rd. plate (counting from periproct) in the proximity of ambitus on 

 abactinal side, corresponding to the appearance of tentacles with discs. 

 Down to the 33rd. plate they occur on alternate plates and form a single 

 row running close to ambulacrum (in., fig. 9). From the 34th. they 

 occur on every successive plate and form two rows down to the 42nd. 

 plate. Plates 43rd. to 47th. have alternately two and three primary 

 tubercles giving rise to five rows (in., fig. 10). Plates 48th. to 55th. 

 with two primary tubercles each, forming four rows. Finally, plates 

 56th. to 62nd. with one primary tubercle each, forming two rows. — ■ 

 Secondary tubercles of interambulacrum : abactinally, up to 10 in a 



