PLATE 103. 



Page 



Fig. 1. Rhynchonella fitchana. 441 



1 a. The dorsal side of the specimen, which preserves a part of the shell. 

 1 b. Profile view of the same. 



Fig. 2. Rhynchonella septata. 443 



2. A cast of the dorsal valve, showing indistinct marks of a few plications near the margin. 



Fig. 3 - 8. Rhynchonella barkandi. 442 



3. Cast of the ventral valve, showing the large muscular impression. The area of the adduc- 



tor muscles is not represented as large as in the specimen. The depression in front is less 

 than one-eighth of an inch below the plane of the more prominent margins. 



4. A similar cast of a smaller individual, in which the form of the rostral cavity is better 



preserved than in the preceding. The casts show a great thickening of the shell at the 

 beak. 



5. Cardinal view of a specimen which is a cast from the interior of both valves, showing the 



great elevation of the dorsal valve, the strong median septum, and the deep sinuosity on 

 each side of the beak. 



6. Front view of the same specimen. 



7. Lateral view of the same, showing the great lateral extension of the dorsal valve. 



8. Profile view of a cast of the ventral valve, showing the abrupt inflection at the margin 



and the expansion of the shell below the beak, which fills the lateral sinuosities in the 

 opposite valve. 



