8 Proceedings of the Royal Irish Academy. 



divide into finer divergent strands. The terminal spicules of these strands 

 spread out in a fan-like manner, and their tips, at least in the preserved 

 sponge, pierce the dermis and project for a short distance above it. The 

 dermal skeleton is an irregular net-work of fibres. These fibres are much 

 more slender than those of the skeleton, consisting sometimes of only two or 

 three rows of .spicules. The pores are seen in the meshes of the dermal net- 

 work ; they vary in diameter from about - 05-0 - 25 mm. 



.—(1) The megascleres are subtylostyli ; they measure 0'35- 



0-45 mm. in length, and have a maximum thickness of O'OOS mm. Their 



:"t is slightly fusiform, and usually slightly crooked. The rounded end is 



sometimes fairly well marked off by a constriction beneath it ; the other end 



tapers to a short point 



il'i Anisochelae of two sizes are present ; the larger form rosettes, which 

 are present : _ numbers both in the dermal membrane and throughout 



the sponge. The smaller anisochelae are also scattered both in the dermis 

 and in the choanosomc. The first-mentioned anisochelae have a rather egg- 

 shaped larger end, as the lower angles of the alae are rounded off, the lower 

 margin of the tooth being rounded of] in the same way. The free portion 

 of the shaft is extrem smaller alae also have rounded corners. 



The length "f the rosette anisochelae U astant, being 0-027-0-03 mm. 



The breadth of the larger ala. t 0'012mm. The smaller anisochelae 



uiilar in 5, but only reach a length of 0*019 mm. 



- 1 contort; th<- ends of the spicule are very 



Blender, and sharply pointed; one is bent in abruptly, while the other has 

 a wider cur outer margin of the spicule is serrated towards both 



a, the ch assigned to the sub-genus 



•11a. Th<^ longer axis of the from OT-0165 mm., and 



the maximum thickness is 0005 mm. The sigmata, which are often in 

 bundles, occur in enormous numbers through the whole sponge. 



i4i T"xa. — The.-' 1 I in small bundles 



in the interior of the sponge. They were not seen in those portions of the 



dermis which were examine'!. The toxa are extremely slender, and arc 



00S mm. in length : the curve in the centre of the spicule is very wide. 



The forej . t Losely allied in spiculation to 'ies, 



2 type species of Paresperella 



Dendy 3 . but differs from it in the greater length of the various kinds 



j] icules, as well as in the shape of the megascleres, as can be seen from 



a comparison of the figure PI .•■ I. fig. 1". b) with that of the subtylostylus 



of the older species given by Professor Dendy (3, PI. XI. fig. _ I. The toxa, 



differ in shape in the two species. 



