SILICIOUS AND HORNY SPONGES WILSON. 393 



2. Oxeas (pi. 48, fig:. 2,5) smooth, slightly curved, with sharp 

 points, 220 by 12 [Jt, with many smaller sizes grading down to the 

 microxeas, are common. The form is sometimes (rarely) that of 

 the style. 



3. Microxeas (pi. 48, fig. 7,c), smooth, slightly bent in the middle 

 (angulated), 30-32 by 2-3 p, common, especially in the dermal mem- 

 brane but also in the interior. Nearly straight forms (fig. 7, e) are 

 also abundant. The stylote form (fig. 7, d) of this spicule also 

 occurs. If we assign the spicule to the group of microscleres, it is 

 only because of convenience of description. For it is connected with 

 the larger oxeas by intermediate spicules of all sizes, which occur 

 abundantly. For such intermediate oxeas the following measure- 

 ments may be recorded : 180 by 10 jx, 160 by 10 [*, 124 by 7 [x, 100 by 

 7 n, 80 by 5 \i, 60 by 4 fx, 40 by 4 jj.. 



4. A good many slender curved oxeas, 40-50 by 1-2 [x, are found 

 in the interior, some of which might be described as toxas (fig. 

 7, /.) The curvature varies; some are bent considerably more than 

 others. The characteristic double curvature of the toxa is occasion- 

 ally acquired, but more often it is only approached, as in the spicules 

 figured where the ends of the bow are nearly straight, not recurved. 



The spiculo-fibers, skeletal tracts, and skeletal lamellae, are com- 

 posed chiefly of the large strongyles, with other megascleres inter- 

 mingled. The dermal reticulum is made up, in addition to the radial 

 tufts of microxeas, of large and medium sized oxeas overlying large 

 strongyles. Spongin, although scanty, is present in the spiculo- 

 fibers and tracts, as is well seen in fragments treated with potash 

 for a minute, just long enough to free the spicules of a fiber from 

 one another and from the spongin. 



Holotype.— Cat. No. 21331, U.S.N.M. 



The genus S Prong ylophora was founded by Dendy (1905, p. 141) 

 for a sponge, S. durissima, taken in the Ceylon seas. Dendy's 

 sponge apparently has no rind, although toward the surface the 

 skeletal reticulum becomes more regular. Thiele (1903, p. 938) has 

 described a sponge from Ternate, to which he gives the name of 

 Petrosia strong glata. The spicules are substantially like those of 

 S. durissima and the Albatross species, and the sponge should be 

 brought under Strongylophora. 



Dendy (190r>) rather doubtfully places his genus in the Gelliinae, 

 where it may be left for the present. Nevertheless the structure of 

 the rind in the species here described is close to that of Coelosphaera 

 (comp. C. toxifera of this report). In both the characteristic por- 

 tion is a dense fenestrated lamella about 0.5 mm. thick. This re- 

 semblance may, to be sure, be only a case of convergent evolution, 

 but it is so striking that I was induced to look very carefully for 

 81709—25 9 



