THE NAUTILUS. 45 



tinct, and close in places, weaker and sparse elsewhere. The 

 summit is decidedly obtuse, as in A. Imosa, the first whorl being 

 nearly planorboid; subsequent whorls are evenly, strongly con- 

 vex. The aperture is very shortly ovate, almost round, its length 

 contained almost 2^ times in that of the shell. Peristome thin, 

 in contrast with the preceding whorl for a short distance. 



Length 4.3, diam. 2,7 mm. ; 5 whorls (type). 



Length 3.75, diam. 2.3, length of aperture 1.35 mm.; 4f 

 whorls. 



Length 4.1, diam. 2.75, length of aperture 1.65 mm.; 4§ 

 whorls. 



Oneida Lake; off Short Point in 8| ft., mud bottom. Lower 

 South Bay, in 18 ft., on mud bottom. 



This species resembles A. limosa in the conspicuously obtuse 

 apex, but differs by the more elevated, turrited spire and the 

 smaller calibre of the whorls, hence smaller aperture. It is 

 also a weaker shell, with more whorls in specimens of the same 

 length. 



There is also an abundant smaller form, resembling the typical 

 form in texture, apex and shape of the whorls, varying in 

 form, but relatively broader than the type. There are some 

 intermediate examples, but as Mr. Baker considers it desirable 

 to have a designation for this form, it may be called A. baker- 

 iana form nimia. The type measures: length 3, diam. 2.5, 

 length of aperture 1.4 mm. ; 4 whorls. 



Amnicola clarkei, n. sp. 



The shell is narrowly umbilicate, conic, a little obtuse at the 

 apex, corneous, nearly smooth. The whorls are very convex, 

 separated by a deep suture, the last whorl tubular. The ape- 

 ture is distinctly oblique, almost circular, the upper end rounded, 

 but a trifle more narrowly so than the base. It projects but 

 little beyond the preceding whorl laterally. The peristome is 

 thin, continuous, scarcely or barely in contact with the preced- 

 ing whorl above. 



Length 3.1, diam, 1.9, length aperture 1.1mm.; 5 whorls 

 (type). 



Length 2.8, diam. 1.6, length aperture 0.85 mm. 



