1879.] MR. F. J. BELL ON ECHINOCIDARIS. 437 



ningham's collection, one of which bears evident marks of having 

 undergone examination. 



It is obvious that the question could not be left in this state. It 

 seemed now necessary to see how far the number of anal plates varied 

 in various species, and whether the character in question had not 

 been definitely attained to by this species only, or whether in other 

 species also there was at times a return to the possession of the large 

 number of plates which are so commonly found in nearly all Echi- 

 nida. 



With this object in view, I have examined all the specimens of the 

 genus Echinocidaris in the Museum ; and the accompanying Table 

 will, I think, show that the work was worth the doing. In addition 

 to the nine specimens here noted, there is a specimen of E. pustu- 

 losa (" grandinosa") in which only three plates are present: one 

 of these is very small ; and it is also evident that two have dropped 

 away. I have been enabled to examine some fifty-four speci- 

 mens in which the anal plates are preserved ; and the " number of 

 specimens " in the following list gives the number of specimens in 

 the set from a given locality or collection. 



Name of species. Locality. 



E. dufresnii Port Otway. 



Shell Bay. 



„ Sandy Point. 



„ Otter Islands. 



E. stellata ? 



E. nigra Coquimbo. 



„ (or sp. closely allied) ? 



, ? 



„ ? 



In the three specimens of E. dufresnii and the one specimen of E. 

 pustulosa (juv.) received from the ' Challenger ' Expedition, the 

 number of anal plates is normal. 



"With regard to this Table we have to note (1) the reduction of 

 the plates below the normal number, as obtaining in three specimens 

 not all of the same species ; (2) that the specimen of E. pustulosa 

 (grandinasa) already referred to, and that of E. nigra from Coquimbo 

 prevent our limiting the possession of five plates to E, dufresnii ; while 

 the specimens with six and with ten plates are most remarkable, inas- 

 much as in both cases there are two plates which retain the proper 

 Echinocidarid character. No normal specimen seems yet to have 

 been observed so young as not to have attained its four anal plates. 

 In conclusion I think it well to abstain for the present from any 

 speculation on the matter, and shall be satisfied if I direct the 

 attention of echinologists to the point in question. 



