Yi sleX, 
PLaTE V. 
Species 10. (Mus. Cuming, in Brit.) 
Hyrra recta, Hyr. testé oblonga, angustd, levigati, 
utrinque alatd, castaned, solidd ; latere postico 
elongato, oblique rotundatim angulato, area post- 
angulari compressa, complanatd, margine dorsali 
recto, depresso, termino producto, acuminato, mar- 
gine laterali inter alam dorsalem et anguli ter- 
profundée excavate; margine ventrali 
recto; latere antico angusto, obliquo, margine 
minum 
dorsali in rostrum acuminatum producto ; um- 
bonibus prominentibus. 
srraiaHt Hyria. Shell oblong, narrow, smooth, 
winged on both sides, chestnut coloured, solid; 
THE 
posterior side elongated with an oblique rounded 
angle; postangular area compressed, flattened, 
with dorsal margin straight, depressed, produced, 
and acuminated at the end, lateral margin be- 
tween the dorsal wing and the end of the angle 
deeply excavated, ventral margin straight ; anterior 
side narrow, oblique, with dorsal margin produced 
into an acuminated rostrum ; umboes prominent. 
SoWERBY. 
Hah. 

(?) 
The greater straightness and depression of the dorsal 
and posterior ventral margins, the greater solidity of 
the shell, the prominence of the umboes and rotundity 
of the posterior angle, may be considered sufticient 
characters to justify separation of this species from 
Hyria avicularis. 

Species 11. (Mus. Sowerby.) 
Hyria syrmaroroora. Hy. testd solidd, brevi, sub- 
trigond, tumidd, utrinque alata, olivaceo-fuscd, 
laevigata, antice subrugatis, intis pallide fulva, 
dentibus centralibus numerosis, divergentibus ; 
elevatim angulato, ared  post- 
angulari depresso, trigono, margine dorsali recto, 
margine 
latere postico 
laterali rectiusculo, termino ventrali 
producto, subacuminato, margine ventrali ante- 
angulum paulo excavato ; latere antico breviusculo, 
margine dorsali recti, in alam parvam producto, 
margine ventrali sursum acclivi ; wmbonibus valideé 
angulatis, prominentibus. 


THE LONG-TRAINED Hyria. 
gonal, tumid, winged on both sides, olive brown, 
Shell solid, short, subtri- 
smooth, slightly wrinkled in front, pale fawn 
within, central teeth numerous, divergent; pos- 
terior side with a raised angle, postangular area 
depressed, trigonal, dorsal margin straight, lateral 
margin rather straight, ventral extremity pro- 
duced, subacuminated, ventral margin a little ex- 
cavated in front of the angle; anterior side rather 
short, dorsal margin straight, produced into a 
small wing, ventral margin sloped upwards; 
umboes strongly angular, prominent. 
Linnus, as recognised by Sowerby, Hupé, &e. 
Hyria avicularis, var. b. Lamarck. 
Hab, River Amazon. 
This shell is much more tumid, elevated, and 
shorter, with a more elevated angle than Hyria avicu- 
laris, with little or no sinus in the posterior lateral 
margin. 

Species 12. (Mus. Lea.) (Copied.) 
Hyria Browntana. Hyr. testd parva, solida, trans- 
versa, rectiusculd, subtrigond, olivaceo-fuscd, lavi- 
gata, utringue alatd, inttis alba ; dentibus anticis 
elongatis, divisis; latere postico ad terminum 
ventralem acuminato ; umbonibus et angulo postico 
tumidis. 
Brown’s Hyrra. Shell small, solid, transverse, rather 
straight, subtrigonal, olive brown, smooth, winged 
on both sides, white within, anterior teeth long, 
divided ; posterior side acuminated at the ventral 
extremity ; umboes and posterior angle tumid. 
Lea. Obs. Unio, vol. ii. page 108, plate 24, 
fig. 116. 
Hab. River Amazon. 

Species 13. (Mus. Brit.) 
Hyrta avata. Hyr. testa obliqu2 subtrigond, levigata, 
olivaceo-fuscd,iridescenti, tumida, altd, breviusculd ; 
latere postico lato, eevatim angulato, bifurcato, 
ala dorsali compressa, laté, verstis terminum valdé 
elevata, margine ventrali rotundato ; latere antico 
breviusculo, angusto, ald dorsali acuminatim pro- 
April, 1869. 
