Knowledge of the Spongida. 347 



next group, viz. Stellettina, and is more than twice the size of 

 the abnormal one (fig. 1, e and I) that accompanies it (see 

 Schmidt's illustration, I c.), which, on the other hand, will 

 be afterwards found to be the normal form in the naw species 

 that I am about to describe under the name of Stelletta reticulata. 

 The entire specimen of Geodia canalicufata, according to my 

 "Notes/ 1 is subglobular, light fawn-colour throughout, and 

 3 inches in diameter, with the vents grouped here and there, and < 

 a thick cortex, chiefly composed of the normal and abnormal 

 siliceous bodies mentioned. 



2. Stellettina. 



With reference to the group Stellettina, the name of 

 which is derived from Schmidt's genus " Stelletta" esta- 

 blished in 1862 (Spong. Adriat. Meeres, p. 46), equivalent to 

 Bowerbank's genus " Ecionemia " of 1866 (Mon. Brit. Spong. 

 vol. ii. p. 4, "type Ecionemia acervus, Bk., MS."), both 

 of whose diagnoses are now remarkably inadequate, the dis- 

 tinction between this and the group Geodina is trenchantly 

 defined if we restrict the siliceous body or ball of the crust to 

 a globular or globo-elliptical form, in which the surface, when 

 fully and normally developed, presents (in all instances that 

 have come under my notice) the tessellated pattern delineated 



m fig. 1, i-h (PL XIV 



£>• 



still 



smaller spine or ray at each angle, all supported on conical 

 processes, which are the circumferential terminations of 

 the delicate linear crystalline segmental radii of which 

 the whole body is composed, and so closely approximated 

 that, but for a shallow groove or interval not more than one 

 third of the diameter of the facet which separates them (tig. k) f 

 the whole would be continuous. Thus it becomes very easy, 

 where there is a crust of such globular bodies, to divide Geodia 

 from those species of Stelletta in which there is none or nothing 

 but a few minute steilates. Hence Schmidt's and Bower- 

 bank's diagnoses of Stelletta are so far sufficient. But there 

 are certain other sponges that have been called " Stelletta" by 

 Schmidt, as well as some new species which I myself am 

 about to describe, which, although presenting, on the one hand, 

 a thin crust composed of discoid bodies otherwise identical in 

 structure with the globular ones of Geodia (ex. gr. Stelletta 

 euastrum, S. discophora, and S. mamillaris, Sdt), and, on 



__ -- 7 



(ex. gr. Stelletta bacillife 



cannot 



globostelliform bodies respectively 



'., n. s 

 diagn 



24* 



