SILICIOUS AND HORNY SPONGES WILSON. 451 



tubercles; and the microstrongyles of the surface are smaller than 

 those of the interior. 



Body vasiform, subspheroidal, somewhat obconical, higher than 

 wide (120 mm. high, 110 mm. across the upper surface). Base flat- 

 tened. Surface with low irregular bosses. Cloaca extending 

 through the body, its aperture on upper surface of sponge 35 mm. 

 wide. Color varies from gray to brown. 



The epactines of the desmas may be simple or bifurcated or may 

 end in flattened extremities, as Sollas has pointed out (1888, p. 285). 

 They are in general distinctly verrucose, sometimes strongly so, 

 sometimes weakly so, and sometimes smooth. The low blunt conical 

 tubercles, sometimes arranged in rings, cover the shaft, and are 

 distinct from the complex tubercles developed in the region of 

 zygosis. In general the zygosis is terminal, as described by Sollas, 

 the skeletal reticulum showing nodal enlargements. But sometimes 

 the tuberculate enlargement extends from the node along the whole 

 side of a skeletal mesh. The union in such a case is no doubt lateral 

 as described by Thiele (1900, p. 53), and as I have been able to 

 observe myself in some instances. The epactines are thicker than in 

 the type, their thickness ranging from 40 to 70 [x. The skeletal 

 meshes vary from 130 by 80 [x to 250 by 250 [x. 



The phyllotriaenes (pi. 49, fig. 10) are larger than in the type. 

 The clads are bifurcate or, not rarely, trifurcate. Width of proto- 

 clad 24^-40 |x, length of protoclad and deuteroclad together commonly 

 about 350 jx. Rhabdome about 100 by 30-40 [x. The phyllotriaenes 

 form a single layer, not several as in the type. 



The skeletal strongyles, 500 by 7-8 [x, lie chiefly in small radial 

 bundles between the subdermal cavities, along with the outermost 

 radially directed beams of the skeletal framework. 



The microstrongyles are abundant in the interior and in the 

 dermal membrane. In the interior the spicules measure 10-22 by 

 2-3 [x, the larger sizes the common ones. The spicules are roughened 

 in the usual way, and the larger ones commonly curved or bent in 

 the middle. In the dermal membrane, with a few exceptions here 

 and there, they measure only 10-12 by 2-3 [x, and are straight or 

 nearly so. 



Holotype.— Oat. No. 21342, U.S.N.M. 



THEONELLA INVAGINATA, new species. 



Plate 43, fig. 2; plate 49, figs. 11, 12, 13, 14, 15. 



One specimen from station D5335. 



Sponge vasiform, tapering below to the attached base; 35 mm. 

 high, 20 nun. across at the upper end. A terminal osculum, 2 mm. 

 wide, leads into a long narrow cloaca having a maximum width of 



