Sponge-fauna of Norway. 433 



cata,^ in which, after an examination of specimens, he asserts 

 the identity of T. muricata with T. Wallichii. The particular 

 grounds on which this statement is made are not given, how- 

 ever, nor is any attempt made to reply to Mr. Kent's objec- 

 tions ; so that one could hardly regard the matter as settled * 

 I therefore wrote to Mr. S. O. Ridley, of the British Museum, 

 asking him to favour me by examining the type specimen of 

 l.\ muricata^ with a view to determining whether it does 

 possess quadriradiate stellates or not. I have to thank him 

 for a valuable letter in reply, and particularly for the following 

 statement, which I venture to quote: — "I have been carefully 

 through with a high power the seven slides which represent 

 the type specimen of Tethea muricata, and find nothing which 

 seems to represent the quadriradiate described and drawn by 

 you in your letter and figured by Wright, of which I have 

 now seen specimens by examining our slides of ^Dorvillia 

 agariciformis^ probably representing the type of that species." 

 After Kent's remarks and this explicit statement I consider 

 that we must regard T. muricata and T. Wallichii as distinct 

 species. In tliis connexion it is worth noticing that the 

 quadriradiate stellates are the last spicules to appear in the 

 development of T. Wallichii; so that very young examples of 

 this species are not distinguishable from T. mur-icata. 



In the " Note," Carter further states that Normania crassa, 

 Bk., Hgmeniacidon jylacentula, Bk., and Eccionema compressa, 

 Bk., are no other than various forms of T. muricata. In 

 order to enable me to examine the truth of this surprising 

 statement, Mr. Norman placed in my hands the type specimen 

 of N. crassa, together with various other specimens, not types, 

 and a type specimen of H. p)lacentula. I find that all these 

 specimens, including both supposed species, agree in every 

 essential detail with one another, but that they are generi- 

 cally different from Thenea, though otherwise nearly allied to 

 it. This was precisely what Mr. Norman predicted. They 

 are without the bifurcated ternate spicules and the grapnels 

 of Thenea, and, on the other hand, possess in abundance a 

 small fusiform roughened acerate which is absent from 

 Thenea. Moreover the structure of their dermis is completely 

 different ; in Thenea it is supported by the long rays of the 

 bifurcated ternates, in Normania by horizontal fascicles of large 

 fusiform acerates, with an occasional triradiate or quadriradiate 

 spicule. These difierences are suflicient to support the generic 

 distinction of Normania and Thenea ; but that they are 

 closely allied is shown by the similarity in the character of 

 their mesodermic tissue, and by the presence in both of the 

 same form of spinispirula ; both likewise are Leptochrota3. 



