INVERTEBRATES. 375 



contracted and produced below ; suture well defined, especially 

 between the lower whorls ; aperture narrow-subovate, a little 

 oblique, acutely angular above; rather narrow, and apparently 

 provided with a small, rounded sinus at the base of the colu- 

 mella below ; outer lip thin and sharp, with a slightly promi- 

 nent margin ; columella arcuate, and somewhat twisted below; 

 inner lip nearly or quite obsolete above. Surface smooth, but 

 showing under a magnifier extremely fine, obscure lines of 

 growth. Length, 1.10 inches; breadth, 0.43 inch; apical angle 

 regular, divergence 30°. Length of aperture, 0.47 inch ; 

 breadth, 0.20 inch. 



This species has much the form and proportions of Macrocheilus fusiformis, 

 Hall (Iowa Report, pi. 29, fig. 7), but seems to be more attenuate, and has a 

 rather more rapidly ascending spire. The figures given by Prof. Hall, however, 

 are from an imperfect specimen, and it is possible that when we can have an 

 opportunity to compare the aperture, it may be found necessary to include these 

 forms under one name, as more varieties of the same species. If so, that pro- 

 posed by Prof. Hall cannot be retained, for the reason that the name fusiformis 

 had been used, by Sowerby, for one of the typical species of this genus. 



The form under consideration may be distinguished from the last described 

 species by its larger size, more slender and more pointed spire, deeper suture, 

 and more convex whorls. We have not seen a specimen with the lip quite per- 

 fect below; the one figured, owing to a fracture of the lip, makes the trunca- 

 tion of the columella appear too distinct, though the lines of growth show that 

 it must be rather distinctly truncated. 



Locality and position : Same as preceding. 



POLYPHEMOPSIS PERACUTA, M. and W. 



PI. 31, fig. la, lb. 



Eulima? peraeuta, Meek and Worthen, October, 1860. Proceedings Acad. Nat. Sci., 

 Philad., p. 466. 



Shell rather large, elongate-conical; spire much elevated, 

 attenuate, very acutely pointed at the apex. Whorls about 

 thirteen, nearly or quite flat, and increasing gradually in size ; 

 last one forming more than half the entire length, slightly 



