HY RR fA. 
Puate II. 
Species 3. (Mus. Brit.) 
Hyria EXAsperata. Hyr. testd subovatd, subcompressd, 
leviter bialata, valde inequilaterali, prope wmbones 
angulatim rugata, versus margines concentricé 
striata ; intis medio cupred, prope margines al- 
bida ; latere postico leviter biangulato, inter angu- 
los complanato, ared postangulari depressd, ad 
marginem dorsalem moderate elevatd, trigond ; 
latere antico brevi, ald parva. 
THE WRINKLED Hyrta. 
= 
Shell subovate, subcompressed, 
slightly bialated, very inequilateral, angularly 
wrinkled near the umboes, concentrically striated 
towards the margins inside, in the centre copper- 
coloured, whitish towards the borders; posterior 
side slightly biangular, between the angles flat- 
tened; postangular area depressed, moderately 
elevated at the dorsal margin, trigonal; anterior 
side short, with small wing. 
Sowersy. 
Hab. British Guayana. 
Although the several corrugated species of S, Ame- 
rican Hyrie are subject to great variations of form, 
the short angular tumid true corrugata is quite 
distinguishable from this and the following species. 

Species 4. (Mus. Brit.) 
Hyria Latiarata. Hyr, testa trigond lata, magna, 
compressa, concentrice rugatd, prope umbones et 
infra usque ad medium rugis magnis obliquis 
divaricatis corrugata ; latere postico expanso, 
obtuse biangulato, ared postangulari in alam tri- 
gonam magnam producta ; latere antico brevissimo, 
angusto, margine dorsali in alam parvam cuneatam 
producto. 
Tue wibe-wincep Hyria. Shell trigonal, wide, large, 
compressed, concentrically wrinkled, near the 
umboes and under as far as the middle corru- 
gated with large oblique diverging wrinkles; 
posterior side expanded, obtusely biangular, with 
postangular area produced into a trigonal large 
wing; anterior side very short, narrow, with 
dorsal margin produced into a small cuneated 
wing. 
SoWERBY. 
Hab. British Guayana. 
This fine species presents a medium in form between 
the preceding and such large flat species of Unio 
as the shell called Alasmodon 
others. 
complanatum and 
April, 1869. 
