382 CHAS. W. HARGITT. 



phonidae would be the only one under which it might be placed, 

 still the family as at present defined, according to Allman 

 (Hydroida, Part II., p. 32), 1 would by no means provide for 

 the species. For example, while there is an axial tubular mass, 

 as shown in Fig. 9, there is no single one of these which bears 

 the hydrothecae as called for by the definition referred to. How- 

 ever, for the time being the species may be left under this family 

 till such time as adequate revision may be undertaken, when the 

 needed modifications may be provided. 



As already intimated, it seems necessary to institute a new 

 genus as well as species for our hydroid. For the genus char- 

 acters the following are designated as diagnostic : 



Colony sponge-like, both in general aspect and in the texture 

 of stems and branches, as well as in growth-habit. Looked at 

 from a short distance it resembles very much our common sponge, 

 Oialina arbuscula, in almost every particular. Hence the pro- 

 posed generic name Keratosuin. The stems arise from a disk- 

 like spongy base and branch much after the manner of " finger 

 sponges." These are composed of a complex and intricate mass 

 of siphon-like tubes which ramify and anastomose irregularly, 

 and from which arise hydrothecae, and nematophoric organs, the 

 latter with thecoid terminal structures similar to the former, the 

 whole cemented together by a dense sponge-like felt of very 

 tenacious and resistant character. Longitudinal and transverse 

 sections of stems or branches show them to be composed of the 

 following parts : (i) a central, axial portion, made up of more 

 or less parallel, anastomosing tubes ; (2) a peripheral portion, 

 composed chiefly of hydrothecae and what may be termed nema- 

 tothecas ; (3) ramifying strands of ccenosarc, which seem to inter- 

 penetrate the elements of the peripheral zone. Figs. 8, 9 and 

 10 will show both the surface aspects as well as sectional views 

 just mentioned. 



Concerning specific diagnosis it must be regretted that the 

 physiological state of the hydroid was such as to afford but 

 meager characters of specific nature. The organism in all the 

 specimens collected seemed to be in a state of hibernation, or 

 better, perhaps, (estivation, no hydranths or similar organs being 



i " Report Chall. Exped.," Vol. XXIII. (part 70), p. 32, 1888 





