(GEOLOGY OF THE FOURTH DISTRICT. 
ORGANIC REMAINS OF THE CHEMUNG GROUP. 
No. 65. —No. 124, page 271. 
Fig. 1 and 1 a. Atrypa dumosa, H. 1 b. Cast of the same. Chemung and Elmira. 
Fig. 2. Atrypa hystrix, H. Bath, Steuben county. 
Fig. 3 and 3 a. Atrypa tribulis, H. 3 b. Cast of the same. Ithaca and Chemung. 
Fig. 4. Atrypa ? tenuilineala, H. Cattaraugus county. 
No. 66. 
Fig. 1 a, b, c, d. Atrypa laticostata, Terebratula laticostata. Phillips (Palaeozoic fossils, 
p. 85, pi. 34, fig. 153). These are all apparently varieties of the same shell, and 
referable to this species. 
Fig. 2. Atrypa laticostata, var. ? This species has six ribs distinctly elevated in front, while 
the other varieties have usually but three ribs elevated. It is probably a distinct 
species. 
Fig. 3. Atrypa. (Species undetermined.) Greenwood, Steuben county. 
Fig. 3 a. Atrypa contracta, H. About three ribs elevated in front. Shell contracted. Green¬ 
wood, Steuben county. 
Fig. 4, 4 a and 4 b. Atrypa eximia, H. This is an abundant form at Ithaca; often associ¬ 
ated in great numbers, but rarely with any other fossil. 
Fig 5. Atrypa polita, H. A very neat shell, with the lower valve much elevated in front. 
Jasper, Steuben county. 
No. 67. 
Fig. 1,1a, and 1 b. Atrypa mesacostalis, H. Shell with from four to six strong ribs along 
the mesial elevation and depression of either valve, while they become obsolete 
toward the margins. The casts are very common everywhere. Ithaca, Che¬ 
mung, &c. 
Fig. 2, 2 a, and 2 b. Atrypa duplicata, H. Shell with two ribs elevated in front, and two 
on each side the mesial fold. Dexterville, Chautauque county. 
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