PLATE 91. 



Page 



Fig. 1, 2, 3. Oethis musculosa. 409 



1 a, b. Dorsal and ventral views of a cast of a small individual. 



2 a. Ventral view of a larger individual, with a small muscular impression. 



2 ft, c. Cardinal and dorsal views of the preceding, showing the cavities made by the brachial 



lamellae and cardinal process, and the impression of the longitudinal crest. 

 3. The ventral side of a cast with narrow and small muscular impressions (perhaps a distinct 



species) . 

 8 a. The cast of a specimen preserving a large and strongly marked muscular impression. 



3 6. A mould from the cast shown in the preceding figure. ( The imprints of the adductor 



muscles are omitted in the drawing.) 



3 e, d, e. Dorsal, profile and cardinal views of the same specimen. 



Fig. 4 & 5. Orthis hipparionyx. 407 



4. The cardinal area, showing the closed foramen. 



5. A portion of the surface of a young shell enlarged, showing the character and direction of 



the strife. 



