ART. 4 SPONGES OF CALIFORNIA DE LAUBENFELS 99 



Remarks. — The nearest approach to the peculiar microsclere of this 

 genus seems to be the sigmas of the sponge described as Dendoin/x 

 ludetisis Topsent (1889, p. xxxvii). 



The closest genus to this one seems to be Amphilectus. This has 

 been used as such a " catch-all," however, that one awaits a revision 

 of it before using it with confidence. The most remarkable micro- 

 scleres afford ample ground for a new genus here, and the other 

 structures are rather peculiar, too. The lack of order and plan, plus 

 spicules partly smooth, partly acanthose yet not showing indications 

 of echinate architecture, together with the palmate chelas and 

 toxas, are all novel. 



Genus ISOCIONA Hallmann 



ISOCIONA LITHOPHOENIX (de Laubcnfels) 



Plocamia lithophoenix de Laubenfels, 1927, p. 263. ' 



Holotype.—U.S.^M. No. 21460; B.M. No. 29.8.22.42. 



Type locality. — Pacific Grove, Calif., intertidal, July, 1925, col- 

 lected by me. The species is abundant in central California, and 

 the University of Southern California had three specimens from the 

 southern part of the State, all without depth record and possibly 

 intertidal. They were taken as follows: Santa Catalina Island, 

 March 21, 1915, and April 1, 1915; and Whites Point (near San 

 Pedro), August 1, 1925. 



Description. — Shape, massive to encrusting. Size, up to 3 cm 

 thick, 10 cm in diameter. Consistency, firm, slightly compressible. 

 Color in life, brilliant vermilion red; preserved, very paie drab. 

 Oscules, rare ; diameter, about 0.5 mm. Pores, not evident. Surface, 

 superficially tuberculate, tubercles 1 to 2 mm high, crowded all over 

 the surface. 



Ectosomal specialization, vague or lacking, except for the dense 

 stand of erect spicules. Endosomal structure, a dense isodictyal 

 reticulation exactly of the Myxilla type, meshes often triangular, 

 cells walled in with ranks of very spiny spicules. If one searches, 

 one finds here and there a few smooth styles, points toward the sur- 

 face. These may be regarded theoretically as vestiges of coring 

 spicules of vanished ascending tracts, the echinating spicules of 

 which have proliferated into ascendency. Our typical Myxillas may 

 have similarly developed from fibroreticulate ancestors. Along the 

 canals leading to the openings mentioned as probably oscular are 

 regions packed with long smooth straight tylostyles. These same 

 spicules stand upright about the apertures and are densely felted all 

 over the surface, together with a few obviously foreign spicules. 

 There is often a layer of the chelas between the tylostyle felt and 



