44 PROF. A. DENDY ON THE 



and two retractor muscles still attached. The tentacles had appa- 

 rently been removed. 



The calcareous ring (PL 6. fig. 62) is very complex, made up of 

 many small pieces, and agreeing minutely in structure with that 

 of Theel's Thyonidium rugosum, as figured in the ' Challenger ' 

 Report. 



The spicules (PI. 6. figs. 63-65), abundantly scattered through the 

 integument, are perforated plates, or, as Theel calls them, " tables," 

 each with a conical central spine or " spire " on one side. The 

 spire is made up of two rods united apically. These spicules 

 differ from those figured by Theel for his Thyonidium rugosiim 

 only in that a great many of them are irregularly quadriradiate 

 in outline. They measure about 0*38 mm. in maximum diameter. 

 The spires appear foreshortened in the figures ; they may attain 

 a length of at least 0-18 mm. 



If Captain Hutton's observations on the number of tentacles 

 were correct, it would seem inevitable that this specimen should 

 form the type of a distinct genus, as he proposed. On the 

 other hand, the detailed agreement of the very complicated 

 calcareous ring with that of Theel's Thyonidium rugosum, which 

 was obtained by the ' Challenger' from near "Wellington, 

 together with the close agreement in spiculation and in external 

 characters, including the pedials, which in both eases are wart- 

 like with retractile ends only, convince me that the two are 

 really identical. The tentacles may easily have been wrongly 

 counted in the first instance, for it is by no means easy to make 

 sure of the number when they are bunched together in spirit 

 specimens. Only the apparent slight diff'erence in spicula- 

 tion then remains to be accounted for, and this is probably 

 more apparent than real and does not amount to a specific 

 distinction. 



Turning now to Hutton's Thyone caudata, we find the original 

 description as follows : — 



" Cylindrical, tapering rather suddenly to the tail ; body 

 rough, covered with papillae, except the posterior end, which is 

 transversely ridged ; tentacula ten, moderate, peduncled and 

 frondose ; dental system large, with five bifid teeth. 



" Eeddish brown, paler at the extremities. 



" Length 2-5 ; breadth -5." 



This species was redescribed by Theel from specimens 

 furnished by Captain Hutton, and in the same work the author 



