28 DESCRIPTION OF 



.(77.7, 3T/.J1 

 PLATE XXVII. 



.ISI28AOA xmnoaA p a!? e 



Fig . 1. ATHYRIS SUBLAMELLOSA. , !a ^ A .,, l 2 



1 a, b. Dorsal and ventral views of a specimen of the ordinary size. 



1 c. Profile view of the same. 



Fig. 2. ATHYRIS SUBQUADRATA. ; 703 



2 a. View of the dorsal valve, and beak of the ventral valve, of a spech. 



men of medium si/e. 



2 b. Ventral view of the same. 

 2 c. Profile view of the same. 



2 d. Ventral view of a smaller and more orbicular form, where the shell is 



exfoliated, showing the vascular impressions. 



,iA 



Fig. 3. RETZIA VERA. 704 



3 a. Ventral view of a specimen, each valve of which is marked by fifty 



costae : a much smaller specimen has forty. 



''<< A .d 8 



Fig. 3. RETZIA VERA, var. COSTATA. 704 



8 b. View of the dorsal valve, showing the beak and broken foramen of the 

 opposite valve. 



3 c. Ventral valve of the same specimen. 



J . 

 Fig. 4. SPIRIFER SETIGERUS. 705 



4 a. View of the dorsal valve, showing the beak of the opposite valve. 



4 b. Ventral valve of the same specimen. 



Fig. 5. SPIRIFER SPINOSUS. 706 



6 a, b. Dorsal and ventral views of this species. 



5 c. Enlargement of the surface, showing the punctate character of the 



shell and the bases of the small spines. 



TT n ' 'fBlft '-n- : ti _ -i . 



Fig. 6. SPIRIPER INCREBESCENS. /Ob 



6 a. Dorsal view of an individual of medium size, with the cardinal extre- 



mities somewhat mucronate. 



6 b. Ventral view of the same. 



6 c. Profile of the same. 



6 d. Dorsal view of an older shell, which is more gibbons, and has the car- 

 dinal extremities less extended. 



6 e &./. Ventral and profile views of an old shell, having the cardinal ex- 

 tremities but little extended. 



6 g. Interior of an imperfect ventral valve, showing the foramen and mus- 

 cular impressions. 



6 h. Interior of the ventral valve of an older specimen, which is more 

 gibbous and the beak more arched. 



6 i. Enlargement of the surface, showing the fine radiating and concentric 

 striae. 



