DESCRIPTION OF 13 



PLATE XII. 



Puge 



Fig. 1 & 2. CHONETES LOGANI. 598 



1 a. Ventral valve of a small specimen. 



1 b. Profile of the same. 



1 c. Dorsal valve of another individual. 



1 d. Enlargement of a ventral valve, showing the character and number of 

 the striae. 



1 e. A further enlargement of the surface, showing the radiating and fine 

 concentric striae. 



2. Interior of a small dorsal valve, showing the vascular impressions. 



Fig. 3. PRODUCTUS FLEMINGI, var. BURLiNaTONENSis. 598 



& 



3 a. Cast of a dorsal valve where the shell .is almost entirely exfoliated, 

 leaving a mould of the exterior. 



3 b. Profile of the same, which shows only a part of the anterior extension 

 of the shell. 



3 c. Ventral valve of the same species. 



3 d. Profile of the same. 



3 e. Cardinal view of the same. 



3 /. Interior of the dorsal valve, showing the cardinal process and hinge- 

 line, the shell below being exfoliated. 



3 g. Enlargement of the fine concentric striae. 



Fig. 4. ORTHIS MICHELINA, var. BURLINGTONENSIS. 596 



4 a. Ventral valve of a specimen of medium size. 



4 b. Enlargement of strite, showing the tubular openings upon the surface. 



Fig. 5. ORTHIS SWALLOVI. 597 



5 a. Ventral valve of a mature individual of this species. 

 5 b. Dorsal valve of another specimen. 



Fig. 6. ATHYRIS INCRASSATUS. 600 



6. The ventral valve of this species. 



Fig. 7. EUOMPHALUS LATUS. 605 



7 a. Upper side of a worn specimen, showing the angular outer margin 

 (the inner volutions imperfect) . 



7 b. Lower side of another specimen, showing the broad shallow umbilicus. 



