ON TWO NEW SPECIES OF ASÏHENOSOMA. 



i 



interposed peristomal ambulacral plates form one or two irregular 

 series. 



Tentacles of abactinal side, as also those situated near or within the 

 peristome, are smaller, more pointed and poorer in calcareous networks, 

 than the remainder of those of actinal side. They are also destitute of 

 calcareous discs present in the latter. Calcareous networks of tentacles 

 show special concentration along two symmetrically situated lines on 

 either side. 



For the distribution and arrangement of large and small tubercles 

 on both ambulacrum and interambulacrum, the reader is referred to figs. 

 8 and 4. 



Ambulacral arch of the perigliatine girdle encloses a somewhat 

 triangular space. The circumferential surface of the arch shows 

 roughness at top for insertion of retractor muscles. On the other 

 surface there is roughness along its inner edge for insertion of the 

 muscle characteristic of the genus. Interambulacral ridge of the girdle 

 possesses two slight prominences. Close observation shows at once 

 that here the ridge is formed of one or two interambulacral plates derived 

 from each of the two rows that compose an interambulacrum, and that 

 each limb of the arch is formed by modification of a single ambulacral 

 plate — a condition that reminds us of what occurs in the Cidaridœ. 

 The sutures between all the plates composing the perigliatine girdle 

 remain distinct. 



Spines perforated, of four kinds : 1) long poison-spines, which are 

 smooth, cylindrical, tapering, of reddish color ; some as long as 60 

 mm. or more ; found scattered all over abactinal side ; 2) stout hoof- 

 capped spines (fig. 7) similar to those generally found in Phormosoma 

 with shaft crenulated in upper part, found on abactinal side from a 

 short distance within ambitus and extending to peristomal margin ; 

 3) small slender spines like poison-spines but more or less crenulated 

 and covered with thicker membrane containing red pigment, occurring 

 intermixed with the two foregoing kinds ; 4) those found thickly 

 crowded in proximity of peristome, densely crenulated and slightly 



