430 Prof. W. J. Sollas on the 



they render it necessary to amend the definition, but fui-nish 

 no excuse for expunging the name of the genus. If every 

 badly -defined genus were liable to a change of name, syste- 

 matic zoologists might as well abandon the task of nomencla- 

 ture altogether. 



Tn 1869, SirWyville Thomson (iv.), in his fine memoir on 

 HoJtenia Cmyenteri^ founded a new suborder, " Leptophloea," 

 with Tisiplionia^ MS., cited as an example. What Tisiphonia 

 might exactly be, there was nothing given to show; the name 

 stands as a word of so many letters, and nothing more. We 

 shall find, however, subsequently that an unfounded attempt 

 was made later to turn it into something more ; but to this 

 we shall refer in due course : we proceed now to the direct 

 subject of this communication, Thenea WaUichii itself. 



In 1<S70, Professor Perceval Wright (v.) gave a full and 

 faithful account of a beautiful little sponge which had been 

 obtained by Dr. Wallich from a depth of 1913 fathoms. This 

 sponge he named, with happy appropriateness, Wyville- 

 Thomsonia Wallichu, thus associating the names of the two 

 preeminent deep-sea investigators with the first-obtained 

 species of deep-sea sponge. It possesses the acerates, bi- 

 furcate-ternate spicules and spinispirules of Thenea, together 

 with large grapnels and some curious few-rayed (one to eight) 

 stellates, not mentioned in Gray's definition. One would thus 

 naturally be led to include it with Thenea, were it not for the 

 two forms last mentioned; and we have now to consider whether 

 these affbrd sufficient reason for generic distinction. If we 

 refer to the value placed on the presence or absence of grap- 

 nels in Qeodia and Stelletta, we shall find that they never 

 serve for more than specific distinction ; moreover, if it be 

 allowable to go beyond Gray's definition and consult the actual 

 specimen of Thenea muricata, we shall find that grapnels are 

 not wanting in it. Then there only remain the pauciradiate 

 stellates ; and these alone will not by any one be considered 

 sufficient to distinguish as different genera species which re- 

 semble each other in every other important character. Thus, 

 unless some considerable undiscovered difference exists between 

 WyviUe- Thomsonia WaUichii and Thenea muricata, we must 

 be content to regard the former as a fellow species with the 

 latter, and so to name it, as Professor Wright (ix.) himself 

 now asserts it should be named, Thenea WaUichii. 



Three months after Professor Wright's paper appeared, 

 Oscar Schmidt partly described a similar sponge obtained 

 from a depth of 178 fathoms off Florida ; he figured some of 

 its spicules, the grapnels and spinispirules, and named it 

 tSteUetta agariciformis. A SteUetta it certainly is not, as it 



