115 
Sect. Il. Placenta; Placenta, Schum. Shell semitransparent, fiat, 
outline suborbicular ; ridges of the hinge very gradually diverging 
from each other, the hinder ridge much the longest. Muscular scar 
rather in front of the middle of the hinge. 
1. Placenta orbicularis, Retz. ; Placuna placenta, Lamk. Hist. N. 3; 
Anomia placenta, Linn. S.N. 1154; Chemn. Conch. viii. t. 79. f. 176. 
cop. E. M. t. 173. f. 2. 
Shell colourless, semitransparent ; when young, pale purplish. 
Inhab. China. N.W. Coast of Australia; Earl of Derby. Port 
Essington. 
The shells vary a little in the inequality of the hinge-ridges, but 
the hinder is always the longest. 
I may remark that Chemnitz gives the best character for the spe- 
cies, and has observed the character furnished by the hinge, which 
has been overlooked by Lamarck, and, as far as I am aware, by all 
recent authors. 
July 25, 1848. 
William Yarrell, Esq., Vice-President, in the Chair. 
The following papers were read :— 
1. DEscrIPTION OF A NEW GENUS AND SPECIES oF SaTYRIDZ. 
By W. Hewrrtson, Esa. 
(Annulosa, pl. 4.) 
The genus Corades, which Mr. E. Doubleday has named and kindly 
characterized for me, comprises but few species of butterflies, most 
of which are of recent occurrence. They are from the mountainous 
districts of Columbia and Venezuela, where, like our European Hip- 
parchias of the same family, they delight in the alpine districts. 
They are remarkable for having the anal angle of the lower wings 
more or less produced into a tail. 
Genus Corapzs, Boisd. MSS. 
Head of moderate width, hairy; maxille about two-thirds the 
length of the body, rather slender. Labial palpi porrect, ascending, 
longer than the head, clothed with hairs and scales, the scales at the 
back of the second joint forming a tuft before the apex. First joint 
short, subcylindric, curved, stoutest at the base. Second joint three 
times the length of the first, subcylindric, slightly curved at the base, 
incrassated towards the apex, which is truncate. Third joint slen- 
derer than the second, about half its length, nearly cylindric, obtuse 
at the apex. Eyes nearly round, not very prominent, smooth. An- 
