446 Zoological Society. 



Genus Rotula. 

 The British Museum series induces me tobeheve that Rotula digi- 

 tata of Agassiz is not distinct from R. Rumphii, as M. Agassiz first 

 considered it to be. 



Genus Echinodiscus. 



I cannot find any permanent difference to distinguish Lobophora 

 hifissa from L. aurita ; they are found together in the same habitat 

 in the Red Sea. 



Genus Mellita. 



The larger spines on the back of this, the former, and succeeding 

 genus are short, equal in size, and furnished with a more or less sphe- 

 rical head. 



The Museum series of specimens show a very gradual passage 

 between the Echini which have been called Mellita testudinaria and 

 M. quinquefora by Agassiz. 



The species which have six slits on the disc are found on the coast 

 of Tropical America, and others on the shores of the Red Sea ; I be- 

 lieve they form two species, which appear to have been confounded 

 under one name. 



The American Mellita hexapora has only narrow linear bands of 

 larger tubercles (bearing the larger spines) between the branched 

 lines radiating from the mouth on the under surface, and these lines 

 are very much branched. 



Mellita similis and M. lobata of Agassiz, also from the West 

 Indies ; the first appears to be only a variety, and the latter a mon- 

 strosity of this species. 



The Red Sea species I have named 



Mellita ERYTHRiEA. 



Shell depressed, with five ambulacra and one posterior interambu- 

 lacral slit ; inferior oral grooves branched, branches very slightly 

 divided ; the larger spines and tubercles in a broad band, occupying 

 nearly the whole interambulacral space between the inferior oral 

 grooves. 



Hab. Red Sea. Sir J. Gardiner Wilkinson. 



There is a new genus which has the edge of the disk perforated 

 and the vent near the mouth, as in Echinoglyphus, but differs in the 

 oral grooves being more simple and only branched near the edge, in 

 the lanceolate form of the ambulacra, and in the square form of the 

 tesserae of the ambulacral zones beyond the tip of the ambulacra. 



Genus Leodia. 



Body depressed, with a posterior slit and five perforations between 

 the end of the ambulacra and edge ; the marginal ambulacral tesserae 

 squarish, like the interambulacral ones ; ambulacra lanceolate, acute 

 at the tip, the anterior one most narrow and longest ; pores united by 

 a groove ; ovarial plate pentangular ; ovarial pores three ; oral grooves 

 simple, slightly impressed, converging towards the margin in front 



