36 
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 ERYTHRZA. 
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 
tesseree of the ambulacral zones beyond the tip of the ambulacra. 
Genus Lrop1ia. 
Body depressed, with a posterior slit and five perforations between 
the end of the ambulacra and edge ; the marginal ambulacral tesserz 
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 
of the ambulacral perforations ; vent near the mouth, in front of the 
anal perforation, with a group of three or four larger spines between 
it and the mouth. 
1. Leop1a RicHARDSONII. 
Body suborbicular, slightly depressed, five-lobed, hinder edge trans- 
verse ; ambulacra lanceolate, not reaching to the discal perforations ; 
