SPON0I1DA. 423 



Hab. Port Darwin, 8-12 fins., bottom sand, mud, &c. ; Arafura 

 Sea, 32-36 fins., bottom sand, mud, and shells : Torres Straits. 



Several dry, more or less imperfect specimens, all somowhat over- 

 grown by Polyzoa, Hydroids, or other Sponges ; and one in spirit, 

 showing the only at all complete extremity. The largest measures 

 155 millim. (6| inches) in present length, and was probably quite 

 250 millim. (12 inches )long when perfect. The species is an extreme 

 form of the same elongate type as R, spathulifera, bnt does not 

 branch, and there is no indication in the present specimens of 

 flattened extremities like those of that species ; the spicule is stouter, 

 longer, and more approaching a cylindrical form than in that species. 



GELLIUS. 



Gray, P. Z. S. 1867, p. 538. 



Asychis, id. I. c. p. 539. 



Desmacodes, Schmidt, Spong. Atl. Geb. p. 64 ; Vosmacr, Notes Roy. 



Mm. Netherl. ii. p. 104. 

 Fibularia, Carter, Ann. fy Mag. N. H. 1882, ix. p. 282. 



The identity of Schmidt's genus with Gray's might appear to be 

 questionable, as Schmidt, besides the acerate and bihamate spicules 

 on which Gray bases his definition, describes also a spinulate and 

 cylindrical one (" Stift ") ; but I fail to find these forms on the slide of 

 the type species which tho Museum possesses from Prof. Schmidt. 

 The genus, which maybe defined as "consisting of massive or erect 

 forms, with loose brittle texture, and a skeleton smooth acerate, and 

 a flesh bihamate spicule," is widely distributed ; the proportions of 

 the spicules vary little, and the external form has chiefly to be relied 

 upon in distinguishing the species. It is unfortunate that Dr. Gray's 

 genus, which, like many others made by him, is sufficiently cha- 

 racterized, and is prior to names assigned to the genus by other 

 authors, has not come into general use, since many svnonyms have 

 been thereby created. Sollas(Ann. & Mag. N. H. 1S82, ix. p. 427) 

 upholds Gray's genus Thenea against all comers in a similar way, 

 and is supported by Norman {apud Bowerbank, Monograph Brit. 

 Sponges, iv. p. 29). 



Horny matter is not usually to be detected in the skeleton. 



58. Gellius conchi, Boiverbanlc, var. ceratina, nov. 



Halichondria couchi, Bowerbank, Mon. Brit. Spong. iii. p. 203, 



pi. lxxxi. tips. 12-15. 

 Halichondria elegantia, id. P. Z. S. 187o, p. 286. 



As Vosmaer (1. c.) has suspected, the above two species are both 

 congeneric with Desmacodes fibulatus (Schmidt, sp.) and agree with 

 it in having a spiculation composed of an acerate and bihamate. 



Bowerhank's type specimen of H. conchi, which I have examined, 

 contains plenty of the latter spicule : and his own statement to 

 the contrary (P. Z. S. 1875, p. 286) is obviously an error, as he 

 himself describes and figures these spicules from this species (Mon. 



