INSTITUTE OF SCIENCE, PHILADELPHIA. 23 



of the large recent species to which this fossil has been casually referred; the 

 last whorl is full and plump, but with the periphery somewhat flatfish, giving 

 a somewhat cylindrical effect ; the aperture is two-thirds as long as the shell, 

 rather narrow ; body with a well-marked callus in adults; pillar with a well- 

 marked twist. Lon. of shell 40, of aperture 27.0; max. lat. of shell 20.0 mm. 



This fine species sometimes retains traces of dark yellow-brown spiral 

 bands on the spire such as are figured by Fischer and Crosse in Aplexa iin- 

 pluviata and A. bjcllida (Exp. Sci. Mexique, Zool., part 7, pi. 39 figs. 5,6 a) 

 of Mexico. The body of the shell seems to have been of a rich orange- 

 brown, if one may judge by the tint remaining. 



At first sight, by the size and acute apex of this shell, the large recent 

 species of Mexico, Aplexa aurantia Carpenter or Maugcria Gray, is brought 

 to mind ; but a comparison of specimens shows that they have little in com- 

 mon. Neither do the other Mexican species now living show any great simi- 

 larity. Though the genus is one noted for mutability, the specimens collected 

 from the Caloosahatchie marls, where they are abundant, associated with 

 Planorbis Conanti and P. Disstoui, are remarkably uniform in character, though 

 few attain quite the dimensions above noted. Some large fossil Physas from 

 Vera Cruz, Mexico, referred by Messrs. Crosse and Fischer to Aplexa nitens 

 Philippi var. gigantea, are more like our shells than the recent nitens, though 

 the Vera Cruz fossil is of a different shape from ours. On the whole, among 

 fossil forms, P. Meigsii approaches Physa bridgerensis Meek, from the Lara- 

 mie, as nearly as any. But compared with a well-grown P. heterostropha of 

 the slender type, the fossil is seen to reproduce almost precisely the outlines 

 of the recent shell, but on a comparatively gigantic scale. The evidence for 

 its relations is thus seen to be indecisive, anO it may quite as well be a true 

 Physa of the heterostropha type as an Aplexa. 



As it does not in the sum of its characters coincide with any described spe- 

 cies, though united to several of them by single characters, I have thought 

 best to give it a distinctive name, especially as it is a prominent member of the 

 fauna in the Caloosahatchie Pliocene. 



There is a rare variety of this species with a short spire, of which two or 

 three specimens were collected, but which exhibits the same microscopic sha- 

 greening as the typical form. 



It is named, at the suggestion of Mr. Joseph Willcox, in honor of Mr. 

 Wm. M, Meigs, of Philadelphia, who accompanied Mr. Willcox in his explora- 

 tions of 1889 and materially assisted in promoting their success. 



