PLEUROCERA. 129 



The aperture is quite rhombic, like Melanin Alexandrensis (nobis). 

 The apical whorls are cariuate and the aperture is about one-fifth the 

 length of the shell. — Lea. 



Figured from Mr. Lea's plate. 



73. P. Estabrookii, Lea. 



Trypanostoma Estabrookii. Lea, Proc. Acad. Nat. Sci., p. 173, 1862. Jour. Acad. 

 Nat. Sci., V, pt. 3, p. 273, t. 3G, f. 80. Obs. ix, p. 05. 

 t 

 Description. — Shell smooth, attenuately conical, rather thin, horn- 

 color; spire very much raised, carinate towards the apex; sutures 



impressed ; whorls about ten, convex ; aperture small, sub- 

 Fig. 242. 

 rhomboidul, whitish within; outer lip acute, subsiuuous; 



columella white and twisted. 



Operculum subovate, dark brown, with polar point near 

 to the basal margin. 



Habitat. — East Tennessee; President Estabrook and 

 Bishop Elliott: near Cleveland, Tennessee; Prof. Christy: 

 and Monroe County, Tennessee ; J. Clark. 



Diameter, -38; length, 1-11 inches. 



Observations. — A number of specimens were received from the above 

 mentioned habitats ; all varying very little. It is closely allied to 

 Christyi herein described, but Avhile it nearly agrees in color, it is 

 usually smaller and has more convex whorls. These are, in some 

 specimens, more inflated on the lower part. It has a strong resem- 

 blance to jH. strigosa (nobis), but is larger and the aperture is more 

 twisted at the base of the columella. The aperture is about one- 

 fourth the length of the shell. I have great pleasure in naming this 

 species after my deceased friend. President Estabrook of Knoxville, 

 from whom I first received it many years since. — Lea. 



Figured from Mr. Lea's plate. Allied to P. subulceforme^ 

 Lea, and to unciale. Ilald. Indeed, in taking an enlarged 

 view of specific values, all these shells would fall into one 

 species. It is a remarkable and suggestive fact, that the exam- 

 ination of specimens from hitherto unsearched localities gen- 

 erall}- tends to diminish the number of species, by furnishing 

 connecting links, rather than to increase them. 



L. F. W. S. IV. 9 



