376 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



The narrowed basal part of the sponge may be simple, the whole 

 sponge pear-like ; or the base may be somewhat irregular showing a 

 tendency to become lobate. There is no root-tuft, but the base is 

 covered with projecting root-processes which hold shelly debris. 



The color is light brown in two specimens, darker in the third. 

 The choanosome is dense. The ectosome is likewise dense, some- 

 what fibrous in its superficial stratum and without radiate cortical 

 oxeas. 



Strong skeletal bundles curve out radially from the center of the 

 sponge to the surface. In the peripheral region, the bundles are not 

 very sharply separated one from the other. Over the general sur- 

 face the superficial spicules project slightly in groups that are quite 

 small, with much dermal membrane between them that shows no 

 megascleres. The radial skeletal bundles are present and alike, both 

 within the limits of the poriferous pits and between the pits. There 

 are no special ectosomal brushes of smaller spicules in which the 

 radial bundles terminate. The extreme basal part of the sponge 

 contains abundant, in fact consists chiefly of, strong, vertically 

 descending spicule bundles that fray out at the lower end. 



Over the surface in general the radial bundles are made up chiefly 

 of oxeas with intermingled protriaenes. Root bundles of the base 

 and lower lateral surface include also many anatriaenes. 



Spicules. — 1. Oxea. Smooth, equiended, tapering gradually to 

 sharp points. In the radial bundles they measure 2.5-4 mm. by 35- 

 50 [x, with smaller, slenderer ones. In the root bundles they reach 

 a larger size, 4.5 mm. by 65 jx. 



Small oxeas, about 250 by 2 [x, scattered through the choanosome, 

 are fairly abundant in two specimens, and almost absent in the third. 

 Probably a detailed examination would show that the different re- 

 gions of one and the same individual differ a good deal in respect to 

 this point, 



2. Protriaene. Common but not very abundant in the radial 

 bundles and the root bundles, less common in one than in the other 

 two specimens. Spicules in the radial bundles have a rhabdome 

 3-4 mm. long, 8-12 \i thick above; clads 24—60 jjl long, 5-7 [x thick 

 at the base. In two specimens, spicules with shorter, stouter clads 

 (34—40 pi long, 6-7 jx thick) predominate. In the third specimen, 

 spicules with slenderer clads (40-60 [x long, 5-6 jx thick) predomi- 

 nate. In this specimen prodiaene and promonaene forms were noted. 



In the root bundles stouter protriaenes occur along with the ordi- 

 nary forms; rhabdome 16-22 jx thick, clads 24-28 [x long and quite 

 thick. Some protriaenes also occur here, of ordinary size, but with 

 clads so degenerate as to form mere protuberances. 



