432 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



Lundbeck's (1905) definition needs some slight alterations. Thus 

 the ectosomal (dermal) megascleres are not always diactinal. They 

 are monactinal for instance, at least as a rule, in the species described 

 below, and in L. tuherosa Hentschel (1911, p. 327) and L. styloderma 

 Hentschel (1914, p. 101). The monactinal form is perhaps, as Hent- 

 schel 1911 (p. 328) suggests, the ancestral one, the diactinal forms 

 derived ones. The variations of the spicule in the species described 

 below support this phylogeny. The isochelas are not always chelae 

 arcuatae, but in some species, L. tuherosa Hentschel and the species 

 described below, chelae palmatae. The chelas may be accompanied 

 not only by sigmas, but by toxas or trichodragmas. (See Topsent's 

 review of the genus, 1901, p. 19.) 



LISSODENDORYX TAWIENSIS, new species. 



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



A specimen from station D51G8 (Sulu archipelago, Tawi Tawi 

 group). Specimen broken but apparently including most of the 

 sponge, which has the shape of a curved lamella, attached and 

 thickened at the base and becoming here cup-like. The lamella is 

 3-4 mm. thick, thinning away toward the upper edge. 



Concave face of lamella riddled with closely set pores about 50 y. in 

 diameter. Through the dermal membrane the main afferent canals, 

 extending more or less radially inward, may be seen. They are 1 mm. 

 or less in diameter and about that distance apart. Outer, convex, 

 face of sponge likewise riddled by closely set small apertures, but 

 these are larger and less uniform than on the concave face, varying 

 in diameter from 100 to 800 [t; they are doubtless the oscula. Effer- 

 ent canals, 1 mm. and less in diameter, extend in radially from this 

 surface, either opening by single oscula or roofed in by an extension 

 of the dermal membrane perforated by several apertures. Embryos 

 are present in the parenchyma, many of them full of short skeletal 

 spicules. 



Skeletal framework a rather loose polyspicular reticulum of spi- 

 nose styles : meshes 3-4 sided, side of mesh about equal to length of a 

 spicule. The spicules forming the side of a mesh number frequently 

 3 or 4, but the common variation is from 1 to 6 ; they form a loose 

 bundle. The bundles forming the sides of the meshes are so arranged 

 as to form some continuous tracts of considerable length. The skele- 

 tal framework breaks up at each surface into loose bunches of diver- 

 gent spicules, which project slightly; such bunches are about a 

 spicule's length apart. Spongin scantily present at the nodes of the 

 skeletal reticulum. 



The ectosomal megascleres are present at both surfaces, some tan- 

 gential, others radial and slightly projecting. The radial spicules are 



