BIVALVE SHELLS. 229 



series, and foiTaing a handsome bending line. Its margin is sharper 

 than that of any other species, owing to the flatness of the shell ; on 

 which account, as it does not appear to have been hitherto described, 

 we would name it anomia compressa. It is from the oolite ; in which, 

 and in the grey limestone, this species and No. 12 are not un- 

 common. 



Fig. 10 represents a large anomia from the second shale. It 

 abounds in the cliffs near Gristhorp ; but is seldom found entire, 

 being generally mutilated at the base. It appears to be the terebra- 

 tula ovoides of Sowerby, Tab. 100; of which his t. lata is only a 

 variety. In the form of the beaks, the gibbous and oblong shape of 

 the shell, the disposition of the striae in the valves, and the absence 

 of undulations at their junction, this shell also coincides with t. digona 

 of Sowerby, Tab. 96; which may possibly be another variety of this 

 species, being often found without the angular projections. As our 

 specimens are almost all either mutilated or compressed at the base, 

 indicating a weakness of structure in that part of the shell, some of 

 them may have had angular projections. The shell is of an olive 

 colour, and has often a smooth and shining aspect, the striae, which 

 are all transverse, being very fine. This species likewise resembles 

 t. biplicata of Sowerby, Tab. 90 ; but has not the folds of that shell. 



No. 14 is very common in the nodules and bands of the alumi- 

 nous strata, both in the sandstone and ironstone. It corresponds in 

 shape with the t. subundata of Sowerby, Tab. 15, Fig. 7 ; being 

 broad and flat, with the margin very faintly undulated. Our shell is 

 somewhat striated in both valves, longitudinally as well as trans- 

 versely. It is often of a considerable size, some specimens being 

 about two inches long, and an inch and a half broad. Sowerby's t. 

 ornithocephala. Tab. 101, is nearly allied to this species, if not the 

 very same. 



3 L 



