80 EIGHA [ID KVANS. 



in it, II tliickly-set layer of ainphidiscs separates it, on the 

 one hand, from the sub-family Spongillinae, and on the 

 other hand places it among the Meyeninae. Again, its 

 generic position is not difficult to determine. The equality 

 of size of the amphidisc rotules separates it from both 

 Tub el la and Parmula, the serrated edge of the rotules from 

 Trochospongilla, the equality in length of all the amphi- 

 discs from Heteromeyenia, and the absence of any kind of 

 filament or appendage, attached to the chitinous tube, from 

 Carterius. Consequently the sponge, which is described in 

 this paper, belongs to the genus Ephydatia. Of the species 

 contained in this genus, the sponge to which the name Ephy- 

 datia blembingia has been given seems to approach 

 Ephydatia plumosa (Carter, 2) more closely than it does 

 any other well-marked species. Several species of the genus 

 Ephydatia are provided with amphioxea, which are covered 

 with small spines, and are the constituent elements of the 

 skeletal fibres. In Ephydatia fluviatilis (17) both smooth 

 and spined spicules occur together. It follows, therefore, 

 that the presence or absence of small spines on the skeletal 

 spicules is not distinctive as a specific character. Potts (17) 

 seems to consider this difference so unimportant that he 

 describes an American sponge, to which he has given the 

 name palmeri, as a mere variety of the Indian sponge 

 plumosa; though the skeletal spicules in the former are 

 covered with small spines, while in the latter they are smooth. 

 The skeletal spicules of Ephydatia blembingia agree 

 with those of palmeri, and not with those of plumosa. 



The amphidiscs seem to be closely similar in plumosa, 

 palmeri, and blembingia, though the rotules appear to be 

 more deeply notched in the two sponges mentioned first than 

 they are in blembingia. If these were all the differences 

 that could be enumerated the sponge now discussed would 

 have to be considered a slight variety of the species plumosa, 

 if, indeed, not actually identical with the variety palmeri. 

 However, there still remains to be mentioned another most 

 important difference, namely, the absence from blembingia 



