﻿SPONGES.-HALLMANN. 



235 



although sometimes slightly subdivided, shows no appearance 

 of having resulted from a coalescence of branches. In some 

 cases, however, a few rope-like thickenings of the lamina, 

 radiating from its junction with the stalk, and calling to mind 

 the main ribs of a palmate foliage leaf, can be traced for a 

 short distance. Scattered over the surface at irregular in- 

 tervals are (sometimes but faintly perceptible) groups of 

 radiately-arranged short ridges, somewhat resembling the 

 "asterisks" of RhaphidophJus typicus var. stcUijcr, but of 

 smaller size ; these do not appear to 

 have any special morphological signi- 

 ficance. The largest specimen measures 



400 mm. in height, 230 mm. in breadth, ^ ^ p 



and 3 to 5 mm. in thickness. 



The original description stands in 

 need of correction in regard to the 

 occurrence of oscula, the dimensions of 

 the spicules and the mode of arrange- 

 ment of the auxiliary megascleres at the 

 surface. 



The surface of the (dry) sponge is 

 everywhere closely dotted with roundish 

 pinhole-like "pores," which are rarely 

 more (and usually much less) than .5 

 mm. in diameter, and stand, on the 

 average, somewhat less than 1 mm. 

 apart. In the type specimen, but not in 

 the present ones, there are in addition 

 to these pores a number of larger open- 

 ings up to 2 mm. in diameter; the 

 latter, however, are due merely to the 

 incomplete coalescence of perhaps 

 originally separated parts. Both kinds 

 of openings appear to ha\e been re- 

 garded by Whitelegge as oscula ; but 

 the latter, as I have just indicated, are 

 purely adventitious, whilst the former 

 are probably of the nature of "sub- 

 dermal pores. " 



The corrected measurements of the 

 spicules are as given in the above 

 diagnosis. It is perhaps scarcely 

 correct to say that the toxa are of two 

 kinds, since there is no difference in 

 shape between the largest and the 

 smallest ; nevertheless indi\iduals of 

 length between 40 jj. and 60 j< are 

 rare. The statement that the auxiliarv 



Fig. 49 — ('. arcuo- 

 pkora. a Principal 

 styles. b Auxiliary 

 subtylo.style. 



