and Acajjulco Sponges. 363 



fig. 31) ; the forks and anchors, being the {so to speak) 

 "■ grappling"- spicules, are of course always concomitants, 

 although not always seen ; while the large acerate body- 

 spicule and the flesh-spicules, viz. the siliceous balls accom- 

 panied by the minute stellates, are also the same. Such is 

 also the spiculation in the six species from the West-Indian 

 seas described and illustrated by Dr. Bowerbank (Proc. Zool. 

 Soc. 1872, '73, and '74), while there is such a sameness in 

 other respects, that if nothing but the form of the specimens 

 is to determine the species, so little dependence is to be placed 

 on this that they may all be set do7/u as the same, subject to 

 variation. 



General Observations. 



The Geodina, like the Esperina, have in most instances so 

 little that is different in their respective spiculations^ that by 

 this alone it is impossible to distinguish them. Size goes for 

 nothing, since a large specimen may have large spicules and 

 a small specimen smaller ones, while in botli the forms are 

 the same. Again, if we search for specific differences in 

 general development and surface-characters, the same species 

 under certain circumstances may assume different forms ; so 

 that, in fact, we have nothing to do but to consider them all 

 as belonging to one species, whatever names may be used for 

 the varieties. Thus the two specimens just mentioned have 

 the same kind of spiculation, although the external or surface- 

 characters differ in the way to which I shall more particularly 

 allude presently. As already stated, the six species from the 

 West-Indian seas, described and figured by i)r. Bowerbank 

 {op. et loc. cit.)y have the same kind of spiculation among 

 themselves, and the same as those from Puerto Cabello and 

 St. Vincent respectively. But Dr. Bowerbank has stated 

 that the porous areas in his G. tuberculosa " appear like a 

 series of impressions made by the point of a pin," while each 

 of the porous areas in G. tumulosa presents a plurality of pores 

 (P. Z. S. 1872, pp. 627 and 629 respectively) ; hence, if we 

 combine the pirdiole pores of G. tuberculosa with the adult form 

 given by Dr. Bowerbank of G. tumulosa^ we shall have just 

 what is to be found in our species from Puerto Cabello, while 

 the plurality of pores in the areas of G. tuberculosa may find its 

 analogy in the specimen from St, Vincent. These facts seem 

 to be repeated in the West-Indian specimens described and 

 illustrated by De F. et M., inasmuch as it is stated of G. gib- 

 berosa^ Lam., that the pores are " punctiformes " (p. 105, 

 pi. XXV. fig. 1 a), and that in their G. caribbcpu the porous area is 

 '' fineraent rdticulec " (p. 106, pi. xxiv. fig. 8). With refer- 



