HyrIaA RUGOSISSIMA. 
THE 
fH Yon tA. 
Prate III. 
Species 5. (Mus. Geale.) 
Hyr. testa transversa, tenui, ovato- 
subtrigond, compressd,incequaliter alata, nigrescenti, 
rugis magnis, oblique divaricatis, irregulariter 
nodosis usque ad margines exasperatd, intis sub- 
ceruled, undulata, dentibus posticis elongatis, 
tenuibus, dentibus anticis tenuibus divisis ; latere 
postico lato, oblique, obtuse angulato, wred postan- 
gulari rugosa, depressd, margine dorsal elevato, ad 
terminum producto, acuminato ; latere antico an- 
gusto, margine dorsali alato, cuneato. 
very ruGosE Hyria. Shell transverse, thin, 
ovately subtrigonal, compressed, unequally winged, 
blackish, roughened to the margins with large, 
obliquely divergent, irregularly nodose wrinkles, 
bluish within, undulated, with the long posterior 
teeth thin, anterior teeth thin, divided; posterior 
side broad, obliquely, obtusely angular; postan- 
gular area rugose, depressed, with the dorsal 
margin elevated, produced, and acuminated at the 
end; anterior side narrow, with dorsal margin 
winged, cuneated. 
SowErpy. 
Hab. 
River Amazon. 
This fourth and last of the corrugated species differs 
from the true Hyria corrugata in its thin substance, 
depressed angle, and oval form. 
In the latter charac- 
ters it resembles Hyria asperata ; but unlike that species, 
it is 
coarsely wrinkled as far as the ventral margin. 
April, 1869. 

HyrIA AVICULARIS. 
THE 
Species 6. (Mus. Brit.) 
HHyr. testa transversd, subcom- 
pressd, oblique ovato-subtrigond, utrinque ine- 
qualiter alata, leevigatd, awreo-subviridi partim 
iridescenti, latere postico oblique producto, rotunda- 
tim angulato ad terminum ventralem acuminato, 
area postangulari complanatd, elevatd, acumi- 
natd, margme laterali concavo, margine ventrali 
postice convexo; latere antico brevi, angusto, 
ala parvd lanceolata; umbonibus haud promi- 
nentibus. 
BIRD-LIKE Hyrra. Shell transverse, subcom- 
pressed, obliquely ovate-subtrigonal, on both sides 
unequally alated, smooth, greenish gold, partly 
iridescent; posterior side obliquely produced, 
roundly angular, acuminated at the ventral end; 
postangular area flattened, elevated, acuminated, 
with lateral margin concave; ventral margin pos- 
teriorly convex; anterior side short, narrow, 
with small lanceolate wing; umboes not promi- 
nent. 
Lamarck. An. 8. vert. Hyria, 1. exclus. var. B. 
Unio caudatus, Wagner. 
Diplodon furcatum, Spix. 
Hyria elongata, Swainson. 
In its young state, as shown in our upper figure, this 
elegantly-formed shell has very produced ale. 
It is 
much more compressed and less angular than Hyria 
syrmatophora. 
