and Acajnilco Sponges. 287 



instead of being confined to the dermal structure, and pos- 

 sessing neither tentacles nor thread-cells, they are thus satis- 

 factorily distinguished from polyps. We already have an 

 instance of this pustuliferous character in Greyella cyathophora, 

 which I described and illustrated several years ago ('Annals,' 

 1869, vol. iv. p. 190, pi. vii.), if not in Schmidt's GribreUa 

 liospitalis also (Spongf. Atlantisch. Gebiet, S. 56, Taf. iv. 

 fig. 12). The parasitic polyp Bergia, with which alone this 

 pustuliform eminence can be confounded, is merely located on 

 the surface of the sponge as a commensal, while the " pus- 

 tuliform eminence " is a part of the sponge itself, connected 

 with the interior by means of a pore-area or excretory canal, 

 like the heads of Cllona coraUinoides &c., whereon, as in 

 many sponges, the radiated arrangement of the spicules per- 

 mits of their being closed or opened as required ; but in 

 Greyella cyathapliora the pore-areas alone are confined to the 

 pustulitorm eminences, while the oscules or vents are present 

 under the common form. Besides this striking character in 

 HalicJiondria pustulosa^ the thick incrustation and the ex- 

 tremely robust, obese form of the equianchorate of which 

 the latter is composed are equally specific. 



Beniera digitata^ Sdt. 



This appears to grow in great abundance about the wharf 

 at Antigua, and when fresh to present a " red" colour, which 

 in the dried state it still slightly retains. The spiculations re- 

 spectively in the mounted type specimens of Reniera dig data 

 and Myxilla anhelans, Sdt., in the British Museum are the 

 same. (See PI. XI. fig. 3, a-c.) 



Phorhas amaranthus, de F. et M. (p. 92, pl. xxi. fig. 1). 



Cauliform, irregularly compressed, repent, straggling, bud- 

 ding into a branch here and there most irregularly, twisting- 

 back upon itself and uniting where in contact, adhering to 

 any foreign objects it may touch during its course of growth, 

 in short, dolng'every thing but growing regularly. Consistence 

 firm. Colour dark-red purple. Surface over the points of the 

 branches or younger parts cancellous or irregularly reticulated 

 in relief, with ti.e lines of the reticulation serrate or jagged, 

 becoming more compact in the older parts, where the dermal 

 sarcode conceals the points of the serrations, so as to leave 

 nothing but a smooth surface of rounded processes with a 

 number of holes, most of which ajjpear to be connected with 

 the branches of the excretory canal-systems, which in accor- 

 dance with the mode of growth, are numerous. Internal 

 structure fibro-cellular throughout, becoming less compact 



