REPORT ON THE MONAXONIDA. 227 



of Mexico, under the name Bursalina muta, var., is really Quasillina at all ; the external 

 form, as figured by him, is somewhat different, and he has not determined, apparently 

 through fear of injuring the specimen, whether a large central cavity is present or not ; 

 this being, though only a post-mortem condition, very characteristic of the species. The 

 species appears to be widely distributed and not uncommon, especially in northern 

 latitudes. 



Zoca%.— Station 49, May 20, 1873; lat. 43° 3' N., long. 63° 39' W.; south of 

 Halifax, Nova Scotia ; depth, 85 fathoms ; bottom, gravel, stones ; bottom temperature, 

 35° '0. Fourteen specimens. 



Habitat. — Shetland (Bowerbank, &c.) ; south-west coast of Norway (Schmidt) ; south 

 of Nova Scotia (Challenger) ; ? Gulf of Mexico (Schmidt) ; Mediteri'anean, ofi" Benzert, 

 North Africa (specimens in British Museum) ; Arctic Ocean (Vosmaer). 



Genus Clio^ia, Grant (Pis. XXV., XXIX.). 



1826. Cliona, Grant, Edinburgh New Philosophical Journa], vol. i. p. 78. 



1833. Vioa, Nardo, Isis, p. 523. 



1866. Hymeniacidon (pars), Bowerbank, Mon. Brit. Spong., vol. ii. p. 212. 



Suberitidfie of boring habit. Spicules tylostyli. 



Our knowledge of the boring sponges and their classification is perhaps in a more 

 unsatisfactory condition than our knowledge of any other group of like importance 

 amongst the Monaxonida. In the first place it appears to us that far too much stress 

 has been laid on the mere boring habit as a character of classificatory importance, and 

 that it is a mistake to group together all the boring sponges as necessarily belonging 

 to even the same subfamUy, while it is quite unnecessary to erect a special group for their 

 reception, like the " Ecccelonida " of Mr. Carter.' 



It appears, however, that nearly all the boring sponges as yet known belong to 

 the Clavulina, but some belong to the family Suberitidse, while others belong to the 

 Spirastrellidse. The name Cliona must be confined to the former group, i.e., to the 

 species with no microsclera. This is the only genus here dealt with, and so we shall 

 not in this place discuss the matter further, merely stating that Cliona is a genus of 

 Suberitidse which has taken to boring habits. 



Cliona dissimilis, Eidley and Dendy (PL XXV. figs. 5, 5a, 5b, 5c, 5d; PI. XXIX. fig. 8). 

 1886. Cliona dissimilis, Eidley and Dendy, Ann. and Mag. Nat. Hist., ser. 5, vol. xviii. p. 490. 



Sponge (PI. XXV. figs. 5, 5a) encrusting and boring into a Madreporarian Coral 

 {Turbinaria sp.). The coraUum of the Turbinaria forms a tabular lamella about 13 mm. 

 thick, now broken into several large pieces. This is coated on both surfaces by a very thin 



1 Journ. Roy. Micr. Soc, vol. ii. p. 496. 



