BIVALVIA. 133 
1. Unio Austentt, Fordes, MS., and Morris. Tab. XX, fig. 12. 
Usro Austentt. Morris. Mem. Geol. Surv., p. 147, pl. 2, fig. 7, 1856. 
Spec. Char. “ Testa oblonga, ovali, modioliformi, posticé obtuse rotundatd ; margine 
dorsali leviter arcuato ; margine ventrali subrecto ; umbonibus feré terminalibus. 
“ An oblong, depressed, modioliform shell, somewhat expanded, and rounded posteri- 
orly; the umbones are depressed and nearly terminal; the surface is but obscurely 
striated.” —Morris. 
Locality. Wempstead. 
The only specimen that I have seen is the one which enriches the Museum in Jermyn 
Street, and on which the species has been established. ‘I'he principal character of dis- 
tinction appears to me to be its inequilaterality, which is im excess. 
2. Unto Epwarpsu, 8. Wood. Tab. XX, fig. 16, a, 6. 
Spec. Char. U. testa elongato-ovatd aut elongato-cuneatd, crassa, trregulariter et con- 
centrice sulcatd vel corrugatd, inequilaterali, convexiusculd ; pedi-regione obtuse rotundata ; 
siphoni-regione valde longiore et obtusé acuminata ; margine ventral subcurvato. 
Shell elongately ovate or wedge-shaped, thick, and irregularly ridged by lines of growth, 
slightly convex or tumid; pedilateral margin obtusely rounded ; siphonal region much the 
longer and roundedly pointed; ventral margin slightly curved. 
Length, 2. iches ; height, 14 inch. 
Locality. Peckham (Ldwards). 
Specimens of this species are few and imperfect, but the form is peculiar, differing 
from that of any other Eocene species; it much resembles U. pictorum, but it is not 
sufficiently pointed on the siphonal side, and it is more inequilateral. One of our figures 
represents a specimen that has lost nearly the whole of the shell, but it gives a very good 
representation of the outward form; and the other figure shows the exterior to have been 
more than usually rugged or corrugated, from which circumstance the specimens have had 
attached to them in Mr. Edwards’s cabinet the MS. name of corrugata, which | should 
have adopted, had it not been employed for a recent species in America. I therefore 
propose for our shell the name of the Author of the ‘Monograph on the Eocene Mollusca.’ 
3. Unio Gisssit, Forbes, MS., and Morris. Tab. XX, fig. 14. 
Unio Giszsit. Morris. Mem. Geol. Survey, p. 147, pl. 2, fig. 6, 1836. 
Spec. Char. “ Testa elongato-ovatd, transversd, utrdque extremitate obtusa, sed posticé 
obscure angulatd ; margine ventrali subrecto. 
