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35 
in the middle ; upper margin rather flattened, with a slight concavity 
at the end of the ambulacra; under side flat near the margin, deeply 
concave in the middle ; spines of the under side near mouth very fine. 
Haé. Australia; N.S.W., Brisbane Water. 
2. EcuINANTHUS TESTUDINARIUS. 
Vent beneath a little within the edge, depressed; back slightly 
raised, evenly convex ; under surface rather concave from the edge. 
Hab. Indian Ocean; Borneo. 
3. ECHINANTHUS OBLONGUS. 
Ovate-oblong, elongate, rounded at the end; sides thick, rounded; 
back depressed round the end of the ambulacra ; crown rather convex; 
ambulacra ovate, lanceolate, broad, and closed at the end ; under 
side concave nearly to the edge; ambulacral grooves indistinct ; vent 
near the margin. 
Hab, Philippines ; Siquijor. 
4. ECHINANTHUS PRODUCTUS. 
Shell ovate, elongate, the hinder end produced and flattened, the 
edge rather thick, thinner behind; the ambulacral petal broad, the 
bands not quite united at the end; under side concave to the margin ; 
vent near the margin. 
Hab. 2 
5. Ecuinantuus Coie. 
Shell ovate, subpentagonal, depressed; margin thick, rounded; back 
depressed as far as the end of the ambulacra, and then rather convex 
in the middle, the under side concave nearly to the edge ; ambulacral 
petal ovate lanceolate, closed at the end; vent near the margin. 
Hab. Mauritius. Lady Mary Cole. 
To those which have a flat base may be added— 
6. EcoHinantuus EXPLANATUS. 
Depressed, much expanded, centre of the back rather convex ; 
ambulacra occupying rather more than half the space between the 
vertex and margin, the lines of pores of the anterior pair and posterior 
odd one far apart at the end; cavity with thin concentric lines of 
short compressed columns near the margin ; jaws depressed. 
Hab. Mauritius ? 
Genus Roruta. 
The British Museum series induces me to believe that Rotula digi- 
tata of Agassiz is not distinct from R. Rumphii, as M. Agassiz first 
considered it to be. 
Genus Ecuinopiscus. 
I cannot find any permanent difference to distinguish Lobophora 
byissa from L. aurita ; they are found together in the same habitat 
in the Red Sea. 
