NORTH AMERICAISr PORIFERiE. PART II. 513 



Variety mollis (PI. xvi, fig. 12). The skeleton is perforated by many large canals open- 

 ing through the upper surface, the tissue between is also very porous, and the aspect is that 

 of a number of fistular sponges united into a more or less complete head. 



Loc, Nassau, in Soc. Coll., and Havana, Island of Noronha, Province of Pernambuco, in 

 Coll. Mus. Comp. Zoology. 



YsLviety 2))'ava (PI. xvi, fig. 17). This variety is similar to the preceding in most of its 

 characteristics, but differs in the entire suppres.sion of the projecting apertures and the 

 smoothness of the surface, broken only by numerous superficial canals. 



Variety disciformis. This is, properly speaking, perhaps one of the typical forms, since 

 the texture is throughout like the best quality of commercial sponges. It may have only 

 one or two large apertures, or it may have several, but they are mostly arranged in a row 

 along the crest of a flattened or helmet-shaped sponge. Its resemblance to disc^ls is lim- 

 ited to this characteristic. It may possibly be identical with Sjjongia musicalis Duch. et 

 Mich. ; the surface appears to agree with that of their dramng. Other specimens, however, 

 which might be best refen-ed to this variety, have not only the helmet shape, but are dis- 

 tinguished by the presence near the oscules of fringe-like tufts. Others, again, have the 

 prominent tufts of primary fibres over the whole surface, with the form of rotunda. 



Variety rotunda (PL xv, fig. 1 ; PI. xvi, fig. 15). In the young this variety may 

 have a conical form, with only one fistular orifice, but generally, either at an early period 

 or later in life, there are several orifices. The rotundity of the form becomes more 

 marked in propoi'tion to the number of these. There are also all grades of full grown 

 forms : those which are almost conical, with only two or three orifices, like the young just 

 described ; those in which the top is almost round ; and those with series of sunken aper- 

 tures dividing the top into radiating ridges, with more or less deeply marked depressions 

 between. The apertures in the round solid heads are not only apt to be more numerous, 

 but also smaller than in any of the other forms. 



Variety aperta. This is precisely similar to the rounded and firmest specimens of the 

 preceding, and like that may have apertures which are either small and numerous, or larger 

 and more sparsely distributed. The intei'ior, however, is cut through by huge channels, 

 which render its solid aspect a mere sham. These channels, or open galleries, penetrate 

 frequently in every dii-ection, anastomosing with each other, and finally opening somewhere 

 upon the sides. They are not to be confounded with the apertures, since they are mere 

 galleries through the substance of the sponge, and are lined by the external membrane. 



Variety corlosiformis (PI. xvi, fig. 14). This name is given in allusion to the form, 

 which has the flattened aspect above, and general outline of variety corlosia, but otherwise 

 it does not reseml^le that species. The colony is in some specimens cavernous, as in the 

 preceding variety ; in others it is solid, the a2)ertures, however, are generally larger, as in 

 the more conical specimens of variety rotunda. 



Variety duplex. This variety is caused by the growth of several long, thick, solid 

 branches, making a peculiar dendritic form. The orifices are large, and situated on one 

 side. The texture of the single specimen examined was a little coarser and darker than 

 is usual in this sub-species. 



Loc, Havana, in Coll. Mus. Comp. Zoology. 



MEMOIRS BOST. SOC. NAT. HIST. VOL. H. 129 



