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VOL. 81 



concavity of the macerated hexactinellid on which this species grew, 

 and therefore impossible to study. The bulk of the sponge was on 

 the outer (convex) part of the hexact, but it ramified extensively into 

 the dictyonine framework. Pores, not evident. Surface, super- 

 ficially smooth. 



Ectosomal specialization, a dermal membrane; very thin, detach- 

 able, fleshy. The dermis contains many of the sigmas, and a few 

 scattered tangential tornotes, and is held up and away from the en- 

 dosome by numerous fascicular bundles of the tornotes, perpendicular 

 to the surface. The Lissodendoryx with which I am familiar in the 

 West Indian region has just such an ectosomal structure. Endosomal 

 structure, " crumb-of -bread," with scattered styles, most of which 

 have their points toward the surface. 



Principal spicules, styles (fig. 43, 5) ; size, about 16ju, by 570/^. Ec- 

 tosomal spicules, tylotes (fig. 43, ^) ; size, about 7/x by 280/u,. Micro- 

 scleres, sigmas (fig. 43, G) ; length, 50;u, to 55/t. 



r^<L^ 



c 



^^<r\ 



Figure 43. — Dissodendoryx rex de Laubenfels, X300 



Remarks. — Generic allocation of this sponge is very difficult, even 

 for a sponge. The ectosome is typically Lissodendoryx and so are the 

 sigmas, but the complete absence of chelas makes one doubt that this 

 genus is the proper one to use. Smooth styles in the endosome are 

 also characteristic of Lissodendoryx., but not styles so much larger 

 than the ectosomal spicules, and the structure is radically different. 

 Lissodendoryx should have monaxons in compact and nearly isodic- 

 tyal reticulation; this sponge has the mycalid structure of many 

 Biemnas. Biemna has similar spiculation, moreover, except for the 

 special dermal spicules, so this could be described as a Bierrwia with 

 the ectosome of a Lissodendoryx. One might erect a new genus, but 

 in view of the scarcity of specimens on hand I regard such action as 

 not at present called for. 



Lundbeck (1905) would make the distinction between MyxiUa and 

 Lissodendoryx that the former has anchorate chelas, the latter arcu- 

 ate or palmate. Wliere the clielas occur this is doubtless the best line 

 of demarcation. In this aberrant form lacking the chelas, however. 

 Lissodendoryx is chosen because, as Lundbeck notes, it usually has 



