o ■> 



7 



they are furnished with hairs in the ordinary way, with stronger spines on the inner face of 

 the segments and on the extremity of the last segments, but the tufts are perhaps not quite 

 so dense as in the other species of Acasta I examined. 



Third cirrus (PI. XXIV, fig. 15) not inconsiderably longer than second, the segments 

 of the pedical being much longer. Rami slightly unequal, of 9 and 10, 8 and 9 segments 

 respectively. The segments 1 — 5 of the anterior ramus are furnished on their inner face, near 

 the upper margin, with a group of short spine-like teeth. The segments 2 and 3 are fur- 

 nished, moreover, with a somewhat stronger tooth-like spine situated beyond the middle of 

 the inner margin and standing off quite horizontally. These spines were not seen, however, 

 in a younger specimen. 



Fourth cirrus (PI. XXIV, fig. 16): the inner margin of the last segment of the 

 pedicel is furnished with a row of 1 2 pointed teeth, which increase in size from the basis to 

 the extremity of the segment. A few smaller teeth are disposed along the main row, increasing 

 in number and size towards the extremity of the segment. The lower segments of the anterior 

 ramus are furnished with a group of strong and partly véry strong spine-like teeth on their inner 

 face and near the upper margin, the teeth standing with their basis up and near each other. 

 In all, 9 of the 14 segments of the anterior ramus were found furnished with such groups of 

 spines, which on the 1 5 segments of the posterior ramus are completely wanting. The seg- 

 ments of the latter ramus are furnished on their inner face with three pairs of spines: one 

 pair of long ones near the outer extremity, a pair of extremely minute ones about the middle 

 of the segment, and a pair not quite so small half way between the two other pairs. 



Fifth and sixth pairs of cirri almost equal, of about 20 segments, which towards the 

 extremity increase in length and at the same time grow narrower. The longest and narrowest 

 segment is about five times as long as broad. The three pairs of spines are of the same size, 

 and are distributed over the inner face of the segments in the same way as described for the 

 posterior ramus of the fourth cirrus. Some of the segments of the 5 th cirrus bear, moreover, 

 a short tooth-like spine, which stands off horizontally from the distal part of the inner face 

 of the segment. 



Note. The description of the 4" 1 to 6 lh cirrus is given from a smaller specimen ; in the somewhat 

 larger one I examined, these cirri were broken off, only three or four of the lower 

 segments being present. 



The penis is long and does not taper so strongly towards the extremity as in A. nitida. 

 It is distinctly ringed ; its distal part is covered with longer and more numerous hairs than 

 in the other species of the genus. 



This species was collected by H. M. S. "Siboga" at: 



Stat. 73. Pulu Barang. Macassar, Spermonde-bank. The depth at which the Sponge containing 

 the Acasta was taken is not given. According to the list of Stations the depth 

 ranges from 45 m. to surface, at 2 miles W. of edge of Spermonde-bank. 



2. Acasta nitida n. sp. PI. XXIV, fig. 17—19. PI. XXV, fig. 1 — 3. 



Carino-lateral parietes about one fourth of width of lateral parietes ; all the parietes 



109 



