20 THE AMERICAN MIDLAND NATURALIST 
* 
Hackberry Group ifi Iowa, especially in the Lower and Middle 
Hackberry. A closely related variety of this species occurs in the 
lower and middle Devonian at Independence, and Pine Creek, 
Iowa. r 
Now in the author’s collection. 
- Airypa stinosa var. lindere N. Var. 
This is a relatively small form, and a well marked western variety 
at least of the New York A.spinosa of Hall; it in fact stands midway 
between certain of the coarse ribbed Atrypas of the western De- 
vonian which have generally been referred to A. reitcularis, and 
the eastern form of A. spinosa. It is much smaller and coarser 
ribbed than the typical forms of this species occurring in the 
Devonian of the Canadian northwest. It is plano-convex to con- 
cavo-cofivex. It has an extreme width of % to 1 inch, is well 
defined and constant in form and expression. 
Position and locality: This form occurs in the lower portion of 
the middle Devonian at Linders quarry 3 miles north from Iowa 
City, Iowa, and is sometimes met with at a few other points in 
Johnson County, Iowa. 
Now in the author’s collection. 
EXPLANATION OF PLATE. 
Fics. 1-2.—Atrypa waterlooensis. N. Sp. 
Ventral and dorsal views of two specimens of this species. : 
Fic. 3.—Altrypa waterlooensis canadensis. N. Var. 
Dorsal view of one specimen of this variety 
Fics. 4-6.—Airypa independensis. N. Sp. 
Fic. 4. Dorsal view of a specimen of this species in the collection of C. L. 
Fenton, showing the normal shape of a rather young shell. Fig. 5: Dorsal 
view of another specimen of this species, showing a less common elon- 
gated form. Fig. 6: Cross-section of a young shell. 
Fics. 7-8.—Atrypa lineata inflata. N. Var. 
Lateral and dorsal views of a very gibbous specimen of this species in 
the collection of C. L. Fenton. From the parting between the two 
nodular Stromatoporoid beds at Charles City, Iowa. 
Fics. 9-11.—Airypa devoniana. N. Sp. 
Dorsal, lateral and dorsal views of three specimens of this species. 
Fig. 11 represents the normal size and shape of an adult specimen. 
Fics. 12-14.—Alrypa owensis. N. Sp. 
Lateral, dorsal and ventral views of three type specimens of this species. 
Fics. 15-16 —Atrypa subhannibalensis. N. Sp. 
Front and dorsal views of the type specimen. 
