216 C. F. LASKBON. 



almost circular in outline. Beaks slightly flattened above, 

 situated at the anterior extremity, overhanging and in- 

 curved. Dorsal and ventral margins approximately parallel, 

 the dorsal with a slight infold, corresponding with an 

 arching of the ventral margin, and giving the whole con- 

 tour a very slight curve. Anterior adductor fairly pro- 

 minent, sub-circular, its cast being sharply ridged upon its 

 ventral margin. Posterior adductor larger, but not so 

 prominent. Pallial line simple. Hinge line probably eden- 

 tulous. Shell moderately thick, and ornamented with close 

 deep concentric growth wrinkles. Xo radial striae at all 

 were discernible. 



Dimensions — Length 2^ inches ; height } of an inch ; 

 depth of one valve f of an inch. 



Loc. Burrier (D). 



Hor. Wandrawandian Series. 



Obs. Several specimens were found, both as casts and 

 with portion of the shell still adherent. Considerable doubt 

 is at present felt as to whether this shell is only a local 

 variety of Plcuroplioms gi-eunriim, or a new species of 

 Stutriihuria. To the former it presents a strong external 

 resemblance, differing however in its somewhat more 

 elongated form, and in its larger size. The original speci- 

 mens of Pleurophoru8 gregurius wen- described from the 

 Lower Marine Series at Farley, and it is naturally to be 

 expected that in the wide vertical separation of these from 

 the Burrier specimens, some evolution would have taken 

 place. The whole question however, seems to hinge on 

 whether the Burrier specimens are Plcu vophonts at all. 

 With considerable trouble the hinge plates of two specimens 

 were partially cleared, sufficiently, however, to show that 

 if the cardinal teeth characteristic of PJeurophorus are 

 present at all, they are smaller than in the type of P. gre- 

 garius. But if, as seems likely, they are not present, the 



