766 MR. A. G. THACKER ON [Juiie 16, 



senting incipient fourth rays. As has been ah^eady stated, several 

 specimens contain some thin hair-like oxea, and in some examples 

 these are quite numerous but in others very scarce ; the latter 

 specimens obviously form connecting links between the typical 

 form of the species and the variety L. canariensis temiijnlosa. 

 These spicules have a thickness of 0"0015 to 0"003 mm., and vary 

 in length from 0'05 to 0"3 mm. ; they are sharply pointed. 



I found no papillae on the inner surface of the Ascon-tubes ; 

 as these structures were present in some and absent in other 

 specimens of Haeckel's L. canariensis (and absent in those de- 

 scribed by Lakschewitsch), this character is manifestly not to be 

 considered as of specific value. 



It remains to discuss the relationship between L. coriacea and 

 L. canariensis. As previously remarked, the only essential dif- 

 ference between them is that L. canariensis has quadriradiate 

 spicules ; but in the Cape Verde Islands examples there appears 

 to be every gradation between specimens in which the quadri- 

 radiates are very numerous (quite 50 °/^ of all the spicules) and 

 other specimens in which they are very scarce, and it is obvious 

 that the latter approach very nearly to L. coriacea. Nor is this 

 all, for A scons having a few quadriradiate spicules have been 

 identified and described as L. coi'iacea. Breitfuss mentions [4] 

 that his L. 7ianseni is very like a sponge described as Ascetta 

 coriacea (n. var. Ascaltis coriacea) hy Fristedt [13] in 1887. 

 Fristedt gives only an incomplete description of this sponge and 

 gives no measurements of the spicules, but he says that the apical 

 rays of the quadriradiates are more slender than the facial lays 

 and are slightly curved. He says that he was doubtful at fii"st as 

 to whether he should identify the sponge as Ascaltis canariensis, 

 but did not do so because (1) of the difierent shape of the apical 

 rays, and (2) of the wide separation of the localities where the 

 respective specimens were found — his sjDonges being arctic. 



Again, in the year 1900 Arnesen [1] described some sponges 

 from Norway which he called Ascetta coriacea, but which had some 

 quadriradiate spicules. 



It must therefore, I think, remain more or less a matter of 

 opinion Avhether L. coriacea and L. canariensis should be main- 

 tained as separate species ; but if they are to be so maintained 

 it is quite certain that these sponges of Fristedt and Arnesen 

 should be called L. canariensis. 



Distribution. Canary Islands {Haeckel [14]) ; Cape Yerde Is- 

 lands {Crossla7id Collection) ; Minorca (Lakschewitsch [16]) ; 

 Ceylon {Dendy [12]) ; Mauritius {Schufner [22]) ; N. Atlantic 

 and Arctic Oceans, and the White ^ea. (Fristedt [13], Arnesen [1], 

 Breitfuss [4] [5]). 



Stcon quadrajstgulatum (Schmidt). 

 Synonymy : — 



Syconella quadrangidata 0. Schmidt [21]. 

 Sycortis quadrangulata Haeckel [14]. 



