PLATE 103. 
Page 
Fig. 1. Riiynchonella 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. Riiynchonella septata. 443 
2. A cast of the dorsal valve, showing indistinct marks of a few plications near the margin. 
Fig. 3-8. Riiynchonella barrandi. 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. 
