PLATE 27. 
1 a - p. SriRIFER MACROPLEURUS. 
1 a. A young shell in which the plications are but faintly developed. 
1 b, c. Dorsal and profile views of a specimen of medium size. 
1 d, & h. Front and cardinal views of the same. 
1 e,f, g. Dorsal, front and cardinal views of a very symmetrical form of medium size. 
1 i. Ventral valve of a specimen of larger size. 
1 k. Ventral view of a larger individual, which is nearly of the maximum size observed. 
1 l. A cast which is somewhat crushed from the base. 
1 7ft, 7i. Interior of the ventral valve, and cast of the same. 
1 o. Part of the exterior of a slightly weathered specimen, showing the extremity of the spire. 
1 p. Enlargement of the radiating striae as seen under a lens upon the surface of ordinary 
specimens. 
