142 THE NAUTILUS. 



new subspecies is not in any way pathological, confirms the claim. 

 The smallest forms mentioned above are as well characterized and 

 symmetrical as the largest forms. 



An interesting fact in regard to the specific value of the bands in 

 this variety is exhibited by two or three specimens. In these the 

 shell is unicolorous until half-grown, and banded from that point to 

 the reflected lip. And one specimen is the reverse in this respect, 

 being banded when young, and later in its growth unicolorous. 

 This would seem to indicate that the bands and color are not even a 

 stable individual character. 



LYMNAEA HINKLEYI N. SP. 



BT FRANK COLLINS BAKER. 



Shell varying from ovate to globose, very thin ; color of periostra- 

 cum light greenish-horn ; surface dull to slightly shining, rough, the 

 growth lines uneven and raised at intervals to form pseudo ribs ; the 

 surface is sometimes malleated and occasionally ornamented by five 

 or six heavy spiral ridges ; fine spiral, impressed lines present and 

 very marked in some specimens ; whorls 3 + (the apex invariably 

 decollated), rounded, tumid in some specimens, the last whorl glo- 

 bose ; spire of variable length but generally shorter than the aperture, 

 broadly conic ; sutures distinctly appressed and frequently distinctly 

 impressed ; aperture roundly ovate, not expanded, acutely narrowed 

 at the posterior angle; outer lip thin, acute; inner lip very tightly 

 appressed to the parietal wall, where it shows as a very thin wash of 

 callus; the anterior part of the inner lip is reflected over the umbili- 

 cus, leaving a very small chink ; axis slightly twisted, forming a dis- 

 tinct ascending plait. 



Length 12, breadth 8.5, aperture length 8, breadth 5 mm. 



Length 11.5, breadth 7.5, aperture length 7.25, breadth 4.5 mm. 



Length 12, breadth 7.75, aperture length 7, breadth 4 mm. 



Length 11, breadth 6.75, aperture length 6.25, breadth 3.75 mm. 



Length 15.25, breadth 9.25, aperture length 10.5, breadth 5.5 mm. 



Length 11, breadth 6.75, aperture length, 6.5, breadth 3.75 mm. 



North fork Snake River, East Idaho. Collected by Mr. A. A. 

 Hinkley in 1905. Types: Chicago Academy of Sciences ; cotypes : 

 Academy of Natural Sciences of Philadelphia, and Mr. A. A. 

 Hinkley. 



