THE SPONGES. • 151 



But when a comparison is made between the three forms /. chclifer ostia- 

 magna, I. lamella, and /. lamella indivisus, it becomes obvious that the chelate 

 character is in itself not a guide to relationship. On the one hand, two 

 s^jonges (/. chclifer and /. lamella) may occur which differ widely in most 

 respects, but agree in having the chelate bipocillus. While on the other 

 hand two sponges (/. lamella and /. lamella mdivisus) occur agreeing in most 

 particulars, but having the one chelate, the other nou-chelate bipocilli. 



lophon indentatus, sp. nov, 



Plate 19, Fig. 6; Plate 30, Figs. 1, 5, 6; Plate 23, Fig. 4. 



Diagnosis. Sponge incrusting, 2-3 mm. thick, fragile, of brown color. Surface in- 

 dented with polygonal collenchymatous depressions 0.5 to 1 mm. in diameter, separated 

 by narrower ridges of more solid skeletogenous tissue. Oscula, 150-200 ft. in diameter, 

 occupy the centres of the depressions. Fores, 75 /a in diameter, scattered over the ridges. 

 Spicules. 1. Spinose style, 220 ix x l-i-lG /*. 2. Subtylote, 220 /x x 8 /j, minutely 

 spinose at extreme ends. 3. Bipocillus, 8 /x, long; smaller end, a curved plate with den- 

 ticulate margins ; larger end, an undivided curved plate of a rounded outline. 4. Ani- 

 sochela, 14 ^ long, palmate. Main skeleton a uniform reticulum of spinose styles. Side 

 of the squarisli or triangular mesh formed by 1, 2, or occasionally 3-4 spicules. 



Station 3405, 3 specimens. 



The sponges are all incrusting upon a Gorgonia. The incrustation is 

 2 to 3 mm. thick, extending in places in the shape of sheets which occupy 

 the axils of the Gorgonia branches. The color is a rather light brown. 

 Sponge fragile, easily torn and broken. 



The surface (Fig. 1, Plate 20) is indented with collenchymatous de- 

 pressions of a polygonal or rounded polygonal outline, 0.5 to 1 mm. in 

 diameter. These depressions, which appear to the eye translucent and 

 gelatinous, are separated by considerably narrower ridges composed of the 

 more solid sponge tissue. A small osculum, 150 to 200 /x, in diameter, lies 

 about in the centre of an area, and in some areas is surrounded by a few 

 other smaller apertures. Between the collenchymatous areas, over the 

 surface of the ridges, abundant pores measuring about 75 /x in diameter 

 are irregularly scattered. The surfoce resembles that of the smooth, 

 reticulate portions of lophon lamella (Fig. 2, Plate 24), but the collen- 

 chymatous areas are considerably smaller and less sharply limited than in 

 the latter species. 



