PLATE I. 
Pigs. 1 — 2. CiiANiA Igxabeuc.exsis, lietzius, p. 7; figs. 1, \a, Id, upper-, side-, and lower, 
views of a perfect specimen, natural size ; Ic, upper view of haemal valve, twice 
the natnral size ; 2, inner view of an imperfect neural valve, natural size ; 
Olapamlii ; Arr'ialoor group. 
Figs. d — 4. Riiyncuoxella mutua, SloUczha, p. 9; figs. 3, 3«, 3i, 3c, ha?mal-, front-, 
neural-, and side-, views of a cast specimen ; 4, neural valve of a larger specimen 
with the shell surface preserved; Sirgtmpore] Ooiatoor group. 
Pig^. 5 — 0. Riiyxchoxella Auuialoohexsis, StoliczJca, p. 10; hasmal-, front-, neural-, and 
side-, views of two perfect specimens, slightly dilfering in size and in the convexity 
of the valves; S. E. of Arr'ialoor ; Arr'ialoor group. 
Fiir. 
V. 
Figs. 8 — 10. 
Figs. 11—13. 
Figs. 14—28. 
Riiyxchoxella compuessa, {LamareJe), p. 11; figs. 7, la, lb, Ic, four views in 
natural size; Id, haemal A-iew of the same specimen, twice the natural size; 
W. of Alldoor ; Trichinopolg group. 
Riiyxchoxella chexieer.a, Stoliczha, p. 12; 8, the largest specimen in the collec- 
tion, partially restored ; 9, a smaller specimen with moderately coarse ribs ; both 
from S, E. of Arrialoor j 10, a well preserved closely ribbed specimen from S. IF. 
of Mulloor ; Arrialoor group. 
Riiyxchoxella xut.vxs, SloUczlca, p. 12; fig. 11, four views of a nearly perfect, 
globose specimen; 12, inner view of the hinge of the neural valv^e; 13, 13«, 
hromal and front views of a large but moderately tumid, somewhat imjierfect 
specimen; S. bg IF. of Mulloor ; Arrialoor group. 
Riiyxchoxella plicatiloi des, SloUczha, p. 13. Specimens representing the gradual 
change at various stages of age ; fig. 19 is the inner view of the apex of the 
haemal valve, with the brachial processes shortened in that view ; 20, the inner 
view of the neural valve with the apical part of the hicmal valve attached to it ; 
fig. 27 represents the most coarsely ribbed specimen. Specimens represented in 
figs. 14, 15, 10, 17, 18, 27 and 28 (the last being a east), are from Olapaudi/, 
Arrialoor group; fig. 22 is from Andoor, and all the remaining from near 
Shulanure, Tricldiiopolg group. 
