196 ANATOMY AND PHYSIOLOGY 



of the coral, and slightly twisted together like a rope. 

 Bark fleshy, granular, strengthened with short cyUndrical 

 spicula. Polypiferous cells scattered, rather produced, 

 wart-like, with a flat radiated tip." (' Proceedings of the 

 Zoological Society of London ' for 1857, page 279.) This 

 description applies only to the singular cloacal appendage 

 to the sponge from amidst which it springs, the structure 

 of the body of the animal being evidently considered by the 

 author as an extraneous mass. The basal sponge is un- 

 doubtedly a portion of the animal to which the part de- 

 scribed by Dr. Gray belongs, the spicula of the elongated 

 cloacal portion being also abundant in the basal mass of 

 sponge ; and the basal mass of the specimen described by 

 Dr. Gray is identical in its structural character with that of 

 the specimen of Hydonema mirabilis in the Bristol Museum. 

 It becomes necessary therefore to remodel the generic cha- 

 racters so as to embrace the leading distinctive structures 

 of the skeleton of the animal, and I propose the following 

 form of description : , 



Skeleton an indefinite network of sihceous spicula, composed 

 of separated elongated fascicuU, reposing on continuous 

 membranes, having the middle of the sponge perforated 

 vertically by an extended spiral fasciculus of single, 

 elongated, and very large spicula, forming the axial 

 skeleton of a columnar cloacal system. 



Type, Hyalonema mirabilis. Gray. 



The construction of the skeleton of the mass of the 

 sponge is intermediate between that of Halichondria pa- 

 nicea and Hymeniacidon caruncula, the respective types of 

 those genera. The network of fasciculated spicula appears 

 never to be definite and continuous as in the former, nor 

 are the skeleton spicula in a dispersed condition on the con- 

 tinuous membranes as in the latter, but are gathered into 

 elongated fasciculi which cross each other in the same plane 

 in every imaginable direction, but without ever appearing 

 to anastomose. The fasciculi vary exceedingly in the 



