SILICIOUS AND HORNY SPONGES WILSON. 421 



millimeter thick; including a single undivided cavity, which is pro- 

 duced into the interior for some distance, as a more or less radial 

 canal. Color of the sponge in general, light yellowish-brown; sec- 

 tions show that the dermal layer of the cortex is colorless and trans- 

 lucent. 



Skeleton of interior, a loose and vague reticulum, in general uni- 

 spicular, the side of a mesh equal to the length of a spicule. The 

 spicules are united by a little spongin, easily demonstrated in sections 

 mounted in water. In the deeper part of the cortical region, the 

 reticular arrangement is more distinct, the sides of the meshes here 

 being polyspicular and stout, often about 50 u, thick. In the dermal 

 layer of the cortex the spicules are closely packed and parallel to 

 the surface, forming a dermal crust 100-200 [i thick. Skeleton of 

 the fistular wall, essentially a continuation of the cortical skeleton. 



/Spicules. — Oxea varying to the strongyle (pi. 48, fig. 10). The 

 spicule is cylindrical, curved or somewhat bent, not always symmetri- 

 cally, and about 200 by 10-14 |a. In the oxea the ends are often quite 

 suddenly pointed but in this matter there is variation, spicules oc- 

 curring with more tapering points. 



The salient characters of the species are the stony surface and the 

 very large number of fistulae. 



Holotype.— Cat. No. 21289, U.S.N.M. 



Family DESMACIDONIDAE. 



Desmacidinae O. Schmidt, 1870, p. 52. 



Desmacidonidae part, Vosmaer, 1S87, p. 348. 



Desmacidonidae plus Heterorrhapfiidae part, Ridley and Dendy, 1887, 



pp. 31, 62. 

 Poeciloscleridae plus H aploscleridae part, Topsent, 1894, pp. 3, 6. 

 Desmacidonidae plus H aploscleridae part, Dendy, 1905, pp. 135, 158. 

 Desmacidonidae plus Homorrhaphidae part plus Heterorrhaphidae part, 



Lundbeck, 1902, 1905, 1910. 



The characteristic microscleres are cheloids (chelas and modi- 

 fications), but forms are included in which these spicules presum- 

 ably have been lost during the course of evolution. 



The subfamilies recognized are the Mycalinae, Phoriosponginae 

 (see George and Wilson, 1919, p. 153), Ectyoninae, together with 

 the Tedaniinae, Desmacellinae, Hamacanthinae, and Merliinae (see 

 previously, under Haploscleridae) . Topsent (19136, p. 52; 1919) 

 would add the Stylotellinae (Lendenfeld 1888) for Stylotella, Sty- 

 linos Topsent (restored), and Semisuberites Carter (type: S. arctica 

 Carter covering Cribrochalina variabilis Vosmaer, Cribrochalina 

 sluiteri Vosmaer, and perhaps other literature species. Topsent, 

 1919, p. 4) , deleting Stylaxia Topsent, 1913. 



