No. 521] SHORTER ARTICLES AND CORRESPONDENCE 305 



walled cells. Externally a shallow radial sulcus in the cellular 

 surface marks the sutures between the plates. Each plate has a 

 triangular smooth median area at the base, where the outer cel- 

 lular layer is lacking, and the arched projecting upper ends of 

 the plates also lack the cellular layer. The summits of the 

 rostral and lateral plates are broader than the bases and strongly 

 arched; the cardinal plate projects less above the cellular 



layer and is lower than the others. Internally the plates of the 

 wall are glossy, show no sheath, and are transversely ridged, the 

 ridges very narrow, parted by wide smooth intervals and about 

 twelve to fifteen in number; the basal fourth or third of each 



P Length of the walls 6.7, diam. 6, height 3 mm. 



The opercular plates protect less than half the area of the 

 orifice, are very thin, glossy, white and smooth both outside and 

 within. They are long and narrow, the terga in contacMnth the 



rounded at the tergal end. 



The cirri are rather short. The first has unequal rami of 8 

 and 12 segments; the rest have subequal rami, the sixth pair 

 having 20 and 22 segments. The segments are armed with two 

 pairs of long spines, and on some of the median segments a third 

 extremely minute pair. Posteriorly there is a pair of small 

 spines at the distal angle of each .segment. 



The penis is about as long as the cirri, very densely annulate, 

 bearing very few minute hairs. There is a dense terminal pencil 

 of very short hairs. 



The mandible lias four large spines and a blunt, mult ispmose 



