BIVALVIA. 133 



1. Unio Austenii, Forbes, MS., and Morris. Tab. XX, fig. 12. 



Uxio Austenii. Morris. Mem. Geol. Surv;, p. 147, pi. 2, fig. 7, 1856. 



Spec. Char. " Testa oblongd, ovali, modioliformi, postice obtuse rotundatd ; margine 

 dorsali leviter arcuato ; margine ventrali subrecto ; umbonibus fere 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. Hempstead. 



The only specimen that I have seen is the one which enriches the Museum in Jenny n 

 Street, and on which the species has been established. The principal character of dis- 

 tinction appears to me to be its inequilaterality, which is in excess. 



2. Unio Edwardsii, S. Wood. Tab. XX, fig. 16, a, b. 



Spec. Char. U. testa elongato-ovatd aut elongato-cuneatd, crassd, irregulariter el con- 

 centrice sulcata vel corrugatd, inaquilaterali, convecciusculd ; pedi-regione obtuse rotundatd ; 

 siphoni-regione valde longiore el obtuse acuminata ; margine ventrali 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\ inches ; height, \\ inch. 



Locality. Peckham {Edwards). 



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 I 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 Gibbsii, Forbes, MS., and Morris. Tab. XX, fig. 14. 



Unio Gibbsii. Morris. Mem. Geol. Survey, p. 147, pi. 2, fig. 6, 1836. 



Spec. Char. " Testa elongato-ovatd, transversa, utrdque extremitate obtusd, sed postice 

 obscure angulatd ; margine ventrali subrecto. 



