New Species of Excavating! Sponge, &c. By H. J. Carter. 499 



against the probable appropriation of these spicules; while the 

 presence of the Esperian rosettes in B. affinis (where they are 

 abundant), and their absence in B. Marshall-Hallii, is met by the 

 facts — first, that when in equianch orates have attained their full 

 development in the rosettes, the latter break up and they are 

 dispersed ; and second, the statement of Dr. Bowerbank that, 

 wherever there are inequi-smchoTSites there may or may not be 

 rosettes. 



EXPLANATION OF PLATE XVIIa. Figs. 1-4. 



Fig. 1. — Rhaphidotheca affinis, n. sp. Pin-like spicule. Scale -^ to ^^^ inch. 



Fig. 2. — R. Marshall-HaUH. Pin-like spicule. Same scale. 



Fig. 3. — Rhaphidotheca affinis. Inequianchorate. a, front view ; 6, lateral 

 view. Same scale. 



Fig. 4. — R. Marshall-Hallii, Inequianchorate. a, front view; 6, lateral view. 

 Same scale. 



N.B. — The pin-like spicule and inequianchorate of Rhaphidotheca Marshall' 

 HalUi, drawn from a fragment of the type-specimen, are introduced here for 

 comparison. 



