460 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



Genus COSCINOSPONGIA Bowerbank (1869). 



Coscinospongia Bowerbank, 1860, pp. 85, 90.— Lendeni eld, 1903, p. 135 

 (synouomy). 



The dermal triaenes are dichotriaenes or derivatives of the same, 

 regarded as mesotriaenes with distal ray but without rhabdome. 



COSCINOSPONGIA THOMASI (Sollas). 



Plate 50, fig. 10. 



Corallistes thomasi Solla,s, 1888, p. 307. 



Coscinospongia thomasi (Sollas), Lendenfeld, 1903, p. 137. 



Station D5513. two specimens: lamellate, ascending in the water. 

 attached below, the free margin rounded. One measures 75 mm. 

 wide, 60 mm. high, about 4 mm. thick. The other is somewhat 

 smaller and broken. Color, light brown. Both sponges considerably 

 larger than Sollas' specimen. 



The sponges show there is no constant relation between convexity 

 and concavity of surface and the distribution of pores and oscula. 

 For in one specimen the pores are on the more convex side, oscula on 

 the more concave, while the opposite is true of the other specimen. 

 The pore areas are small circular depressions about 1200 ;x in diameter 

 and 0.5 mm. apart. In the center of the area, in a few cases, a minute 

 aperture, the pore, has remained open. The very similar oscular 

 areas on the other side are somewhat larger, about 300 y. in diameter 

 and 1-2 mm. apart, Again, in a few cases, a minute aperture, the 

 osculum, has remained open in the center of the area. 



The spicule measurements are close to those given by Sollas (1888). 



The desma (pi. 50, fig. 10) shows the characteristic fungiform 

 tubercles, some of the tubercles on the most peripheral desmas sup- 

 porting the dermal membrane along with the cladomes of the 

 triaenes. The length of a developed desma is 400-500 pi. thickness of 

 middle body, epirhabd. 30-35 p.. There are several clads. reaching 

 175 jjl in length, and the spicules present bold curves which help to 

 bound different skeletal meshes. The tubercles are for the most part 

 simple, or there, are two or three closely juxtaposed tubercles on the 

 same stalk, or the tubercle may be indented as if subdividing. Range 

 in width of tubercle 24-50 [x. 



In the d idiot riaene, the rhabdome measures 210-280 by 28-35 |i; 

 primary clad 28-35 [x long and about as wide: secondary clads 65-100 

 [i long, not always alike in same spicule, sometimes irregularly curved. 

 Margins and upper surface of clads uneven, about as in Sollas' 

 specimens. 



Very slender rhabd spicules occur on the pore side of the sponge. 

 They lie in the ectosome. radial to the surface and projecting beyond 



