British Species of Sponges. 337 



the specimen there alluded to was that which was described 

 and conjecturally referred to M. armata by Mr. Carter in 

 1874 (Ann. & Mag. Nat. Hist. (4) xiv. p. 457). This state- 

 ment thus concurs with Mr. Carter's figure {J. c. pi. xxi. 

 fig. 27) in fixing the shape of the toxite, and, together with 

 the practical coincidence of the spicular measurements, clearly 

 identifies the sponge described in 1874 with Microciona strep- 

 sitoxa. 



The occurrence of so marked and striking a spicular form 

 in these two sponges cannot but arrest the attention. Its 

 connexion with other forms of toxa seems plain, and it is 

 easy to imagine how it may pass into them ; indeed the 

 smaller form of toxite in M. strepsitoxa (which I have not 

 observed in A. foliatus) appears to be an intermediate form 

 between it and the spined toxa, which are of frequent occur- 

 rence in sponges of similar spiculation ; yet the long-armed 

 form is sufficiently distinct to make it highly improbable that 

 the two sponges whicli contain it should be otherwise than 

 closely related to one another, more closely, perhaps, than is 

 either to any other known sponge. At present these two 

 sponges find themselves not only in different genera but in 

 different subfamilies ; the skeletal structure of A. foliatus^ 

 however, but for the absence in it of the spined ecliinating 

 spicule, agrees most closely with that of some forms of Clathria 

 (e.g. C. compressa^ O. S., Sp. des A. M. Taf. vi. fig, 1), and 

 no doubt A. foliatus would find its most natural place in that 

 Ectyonine genus, the presence or absence of the echinating 

 spined style being apparently in this case also, as it is stated 

 by Messrs. Ridley and Dendy to be in the genus Myxilla 

 ('Challenger' Monaxonida, p. 129), of comparatively little 

 importance. 



The intimate interconnexion which exists between the 

 genera Clathria^ Microciona^ and Rliapliidopliliis is obvious 

 from the remarkable correspondence of their spiculation, inde- 

 pendently of the points of resemblance in their skeletal struc- 

 ture. It is perhaps a question of appreciation and convenience 

 (c/! 'Challenger' Monaxonida, p. 151) whether their generic 

 separation should be maintained ; to unite them, if permissible 

 on other grounds, would be to get rid of some of tiie difficulties 

 which beset this group of sponges, and the consolidated genus 

 would form a nucleus, around which it may be that other 

 sponges of not very different spiculation would be found to 

 group themselves naturally. 



Returning to the peculiar toxite of M. strepsitoxa, I have 

 to mention the interesting fact that Mr. Carter lias quite lately 

 found at Budleigh Salterton a piece of chert from the Upper 



