APPENDIX. 241 



kinds chiefly confined to the surface, where they are 

 arranged vertically with their heads toward the dermal 

 layers and their shafts internally; the stellates, although 

 most numerous and packed together crust-like in the 

 dermal layer, are also scattered throughout the body- 

 substance; while the sheaf-like bundles of minute 

 acerate spicules are entirely confined to the latter. 



Habitat. Budleigh-Salterton (Carter). 



I am inclined to think that Stelletta lactea of 

 Carter may be synonymous with Tethya Collingsii, 

 Bowerbank ; but Carter figures the two forms of 

 stellates as of equal total diameter, whereas in T. Col- 

 ling sii the long rayed form is some three times the 

 diameter of the short rayed, and has far fewer rays ; 

 in T. Colling sii 9 moreover, the bifurcating trifid 

 spicula are few and are evidently a mere variety of the 

 recurving trifids. 



4. RENIERA PARFITTI, Bow. 



Reniera Parfitti, BowerbaBk. In Parfitt Marine and Freshwater 

 Sponges of Devonshire. Trans. Devon. Ass. Advanc. Liter. 

 Science and Art, 1868, p. 10. 



" Massive, sessile ; surface smooth, somewhat undu- 

 lated; oscula simple and sparsely distributed, slightly 

 raised above the surface ; pores inconspicuous to the 

 unassisted eye ; dermal membrane abundantly spicu- 

 lous ; spicula very irregularly disposed, imbedded in 

 the membrane ; spicula acerate, stout, with a few more 

 slender ones intermixed, of two sizes ; skeleton spicula 

 very numerous, acerate, stout, suddenly and acutely 

 pointed, -nfeotib- of an inch long and ywoth of an inch 



VOL. iv. 16 



