254 MR. F. J. BELL ON THE ECHINOIDEA. [Mar. 4, 



Before discussing the relation which il/eo?«a and B?-issus hold to one 

 another, it is necessary to refer to the subgenus 3Ietalia, under 

 which are included the four species africana (Verrill), maculosa 

 (Gmelin), peetoralis (Lanik.), and sternalis (Lamk.). 



Of this last-named species there are in the possession of the 

 Museum three examples bearing Dr. Gray's label of Brissus ster- 

 nalis. Two of them are injured, and are apparently the specimens 

 a and c of Gray's Catalogue ; they are about IGO millims. long, and 

 have the vertex considerably elevated. The third specimen, which is 

 well provided with spines, is not more than 100 niihims. long; 

 and no part of the abactinal surface is raised above the general level. 

 Prof. Agassiz (p. 145) credits the Museum with specimens from 

 Raine's Inlet, Tort Essington, Reef Attagor, Luz^^n, and Osmaga 

 {sic) ; all these, with the exception of that from Luzon, are young 

 examples of Brissus unicolor. The Luzon example seems, however, 

 to belong to Metalia, and may well be the young of 31. sternalis ; 

 were it not for the third of Gray's specimens above mentioned it 

 would be impossible to connect this young form with the large 

 examples. Those in the possession of the Museum incline me to 

 accept Agassiz's account of the changes in this species during 

 growth ; but an anxious look-out must be kept for fresh specimens ; 

 none have yet been received from the collections made by the 

 'Challenger' Expedition. 



Agassiz distinguishes Metalia as a subgenus thus : — " The sub- 

 genera Plagionotus and Metalia are united as a single subgenns 

 of Brissus {Metalia), the slight difference in the course of the 

 peripetalous fascicle and the presence of larger tubercles not being 

 sufficient ground, with our present knowledge of the changes due 

 to growth, to warrant retaining them both ; and as Plagionotus is 

 already in use among Coleoptera, the subgenus proposed by Gray 

 has been adopted and amended to include Brissidse having a more 

 or less broad, elliptical, or undulating re-entering peripetalous fas- 

 cicle, and an anterior ambulacral groove." I fear I must take ex- 

 ception to this lucid diagnosis ; not only is the odd anterior ambu- 

 lacrum of M. maculosa said (p. 599) to be "flush with the test, 

 except towards the ambitus, as it approaches the fascicle, and below 

 it when it is placed in a slight indentation of the test," but a com- 

 parison of the " deep " groove of ill. sternalis with the slight groove 

 of M. maculosa and M. peetoralis on the one hand, and on the 

 other a comparison of the anterior ambulacrum in Brissus and 

 Meoma, in which at times there are slight indications of depressions, 

 will be sufficient to show that this character is not of more than 

 specific importance, at any rate. I have, indeed, some hopes of 

 showing that this depression of the anterior ambulacrum is a cha- 

 racteristic of the more lately developed forms ; but for the present 

 I must be content to remark that in the Brissine series it is only 

 found in forms which, by the elaborate character of their subanal 

 fascicle, indicate their later appearance. 



This subanal fascicle displays the following arrangements : — In 

 Meoma it is a narrow band, which does not extend beyond the ac- 



