300 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



Subfamily Tethyopsinae. 

 Tethyopsinae Lendenfeld, 1906, p. 253. 



With a special cloacal tube. 



In addition to Tethyopsis, the subfamily includes the following 



genera: TrihracMon Weltner (1882, p. 50) {-^Tribrachzum, Sollas 



1888, p. 153) . (See also Lendenfeld, 1903, p. 67 ; Lendenfeld, 1906, p. 



253). Disyringa Sollas (1888, p. 161). (See Lendenfeld, 1906, p. 



290.) 



Genus TETHYOPSIS Stewart (1870). 



Tethyopsis Stewart, 1870, p. 281. 



The cloacal tube contains several excurrent canals. Without sani- 

 dasters. One of the euaster forms may be slightly modified in the 

 direction of a streptaster. Trichodragmas may occur. 



TETHYOPSIS DUBIA. new species. 



Plate 37, fig. 4 ; plate 45, figs. 12. 14, 15. 



One specimen from D5163. 



Sponge spheroidal, 15 mm. in diameter, attached to a shell on one 

 side and much incrusted with shelly debris. The cloacal tube pro- 

 trudes about 5 mm. It is 5 mm. wide at its base, slightly narrower 

 at the free end. It contains four equal longitudinal canals, each 

 about 1.5 mm. in diameter, all freely open at the upper end (in the 

 actual specimen). The walls of the canals are very thin. They 

 are plainly distinguishable from one another in cross section of the 

 tube and are marked off from one another on the surface of the 

 tube by slight longitudinal furrows. Thus the entire cloacal tube 

 presents the appearance of being a fusion of four subsidiary tubes. 



Pores are abundantly scattered over the surface of the body, which 

 is somewhat uneven owing to the fact that the dermal membrane 

 is elevated on the points of the cladi of the triaenes. The ectosome 

 forms a very distinct translucent layer about 600 [x thick, which 

 includes large subdermal spaces. The ectosome is fibrous in its 

 outermost portion, and again where it borders upon the choanosome 

 it includes a fibrous stratum, about 175 pi thick. 



The radial megascleres, chiefly plagiotriaenes, proceed from the 

 center to all points of the surface. They are so abundant as not 

 to form distinct bundles. The system of radial triaenes is con- 

 tinued into the walls of the subsidiary cloacal tubes, but the spicules 

 are here modified into orthomonaenes and orthodiaenes, the rhab- 

 domes lying longitudinally, the cladi extending circularly, in the 

 tube wall. 



Spicules. — (1) Plagiotriaenes (pi. 45, fig. 14), small; clads 175- 

 300 n long, strong ; rhabdome 3.3-4 mm. long, about 90 \l thick. The 

 clads lie at the surface, supporting the dermal membrane, also in 

 the deeper layer of ectosome below the subdermal cavities. Younger 



