SILICIOUS AND HORNY SPONGES WILSON. 431 



be so aliened as to give rise to continuous, but inconspicuous, tracts ; 

 best developed of these are radial to the surfaces and help to bound 

 the main canals. 



The ectosomal megascleres, slender tornotes, are abundant; 

 tangentially and radially arranged at both surfaces of the sponge, 

 the radial spicules slightly protruding and for the most part in 

 closely set divergent brushes. Round the oscula, the tornotes are 

 especially abundant; they here form tangential sheaves. 



Spicules. — 1. Skeletal style (pi. 49, fig. 3, a), smoth, cylindrical, 

 slightly curved near basal end, 270-300 by 18-21 \l. 



2. Ectosomal tornote (fig. 3, ft), smooth, straight, 165-200 by 6-7 [x. 



3. Sigma (fig. 3, c), 50-70 y. long but ranging down to 10 \k long; 

 the larger abundant in the interior, the smallest common in the 

 dermal membrane as well as in the interior. 



4. Ancora (pi. 49, fig. 4, «, b), 40 [x long ranging down to 10 pi 

 long; abundant in dermal membrane of both surfaces, present but 

 less abundant in the interior. The spicule is the usual tridentate 

 isancora. There is just a suggestion of an angulation in the middle 

 of the shaft (fig. 4, a) ; alae are longer than the teeth. In an apical 

 view the spicule presents a neatly symmetrical, four-parted, crosslike 

 figure, the shaft with the thin lateral expansion on each side (ala) 

 just opposite the middle tooth and in this view looking not unlike a 

 tooth, the lateral teeth opposite each other. (Compare such figures 

 as 17&, pi. 21, Ridley and Dendy, 1887.) 



This species is very close in its spiculation to M. lacunosa Lambe 

 from the extreme eastern Pacific (west coast of Vancouver Island, 

 Lambe, 1893, p. 70), a massive sponge with sigmas about 19 \l long. 

 In its lamellate character and in respect to the classes of spicules 

 presented, the species also resembles M. hastata Ridley and Dendy 

 (1887, p. 134) from the Atlantic coast of South America, but the two 

 are far apart in respect to the size of the megascleres and in some 

 other points. 



Genus LISSODENDORYX Topsent emended Lundbeck (1905). 



Amphilectus part, Authors. — Part, Vosmaeb, 1887, p. 353. 

 Myxilla Schmidt part, Dendy, 1895, p. 29 ; 1905, p. 168. 



Lissodendoryx Topsent 1892 ; 1894c, p. 9 ; 1901, p. 19.— Lundbeck, 1905, p. 

 153.— George and Wilson, 1919, p. 150. 



Skeletal framework reticular, including sometimes well-marked 

 fibers, or dendritic; spongin present in variable amount. Skeletal 

 megascleres generally smooth styles, but sometimes spined. Special 

 ectosomal megascleres present; these generally, but not always, di- 

 actinal. Microscleres isochelas, never ancoras; these may be accom- 

 panied by sigmas, toxas, or trichodragmas. 



