430 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



used in the sense of Myxilla, Topsent olim. According to this propo- 

 sition, the names, Myxilla and Dendoryx, of Topsent's classification 

 would simply be interchanged. 



Lundbeck and Levinsen (Lundbeck 1905, pp. 2-7) find that an- 

 coras and chelas are sharply separated — that is, there are no tran- 

 sitional forms. On this basis they would separate genera with an- 

 coras from those with chelas. Lundbeck applies this principle, ac- 

 cepted by Kirkpatrick, Topsent, Hentschel, George and Wilson 

 (1919), to the case of Myxilla (Dendoryx formerly) and Lissoden- 

 doryx. These two genera intergrade with respect to the character 

 (spinulation or smoothness of megascleres) on which they were 

 originally separated by Topsent. Lundbeck redefines them on the 

 basis of the microscleres, assigning species with ancoras to Myxilla, 

 species with chelas to Lissodendoryx. 



Considering the very great resemblance between Myxilla and Lis- 

 sodendoryx tawiensis of this paper, and other similar cases, I wish to 

 say that it seems to me artificial to place such species in different 

 genera. It would be preferable, to list the two sets of species as 

 subgroups of Myxilla, frankly defining them as groups based on a 

 single character and therefore probably artificial. Rather, however, 

 than disturb at present this current tendency in classification, I 

 make use of the two genera. 



MYXILLA CRUCIFERA, new species. 



Plate 42, fig. 5 ; plate 49, figs. 3, 4. 



Station D5168, one specimen. Sponge a concavo-convex lamellate 

 fragment, about 40 by 50 mm. and 5-8 mm. thick. The convex 

 surface bears the oscula, 1-2 mm. in diameter and 2-4 mm. apart, 

 from which the main efferent canals, about as wide as the oscula, 

 extend radially inward. The concave surface is very irregular, 

 presenting a cup-like depression; dermal membrane of this surface 

 uniformly perforated by the closely set pores. Through this sieve- 

 like membrane the main afferent canals, less than 1 mm. in diameter 

 and about 1 mm. apart, may be seen extending radially inward, thus 

 making the impression of pore areas separated by nonporous tracts. 

 Color, light brown ; sponge firm. 



Main skeleton a polyspiculaf reticulum formed by smooth styles; 

 meshes 3 or 4 sided; side of a mesh about equal to the length of a 

 spicule; bundle forming the side frequently includes 6-8 spicules 

 but the number ranges down to two or three. Spicules bound 

 together at nodes of reticulum by ;i little spongin. Bundles of 

 spicules forming the radial sides of the most superficial meshes very 

 commonly project slightly: Sides of the meshes in the interior may 



