THE CYCLOPHORID LAND MOLLUSKS OF AMERICA 183 



diameter, 36 mm. U.S.N.M. No. 429586 contains three specimens 

 collected by H. Pittier at an elevation of 550 meters in the vicinity 

 of Secanquin, Alta Vera Paz. U.S.N.M. No. 185499 contains another 

 specimen from the same locality. U.S.N.M. No. 355368 contains two 

 specimens collected by A. A. Hinkley at Chama, Alta Vera Paz. 

 There are six additional lots without specific locality. 



This species differs from M. j)alenquensis (Pilsbry) in being much 

 larger. 



MEGACYCLOTUS PALENQUENSIS (Pilsbry) 



Plate 24, Figukes 16-18 



1935. Aperostoma (AmpMcyclotus) paJcnqucnse Pilsbry, Proc. Acad. Nat. Sci. 

 Philadelphia, vol. 87, pp. 3-4, pi. 1, figs. 3, 3a, 3b. 



Shell depressed-helicoid, covered with a wood-brown periostracum ; 

 when denuded the last whorl is yellowish white and the rest rose 

 colored. The nucleus consists of a little more than one turn, which 

 is well rounded and smooth. The succeeding turns are well rounded 

 and marked by decidedly retractively curved threads, which are about 

 as wide as the spaces that separate them. These threads and the 

 spaces between them vary in strength, and the surface has a some- 

 what pitted or dull rasplike appearance. Suture well impressed. 

 Periphery well rounded. Base openly umbilicated, well rounded, and 

 marked by the same sculpture as that characterizing the spire, only a 

 little less strongly developed. The umbilicus is similarly sculptured. 

 Aperture circular, decidedly oblique, drawn out into a very conspicuous 

 angle at the posterior angle. Peristome simple ; the outer somewhat 

 expanded and reflected; the inner evenly curved, forming with the 

 callus of the parietal wall, a regular sigmoid outline. 



The type, Acad. Nat. Sci. Philadelphia No. 106344, was collected by 

 Dr. Dolley in the District of Palenque, State of Chiapas, Mexico. It 

 has 5 whorls and measures: Height, 20.7 mm.; greater diameter, 

 34 mm.; lesser diameter, 25.9 mm. A paratype bearing the same 

 number has 5.4 whorls and measures: Height, 21.7 mm.; greater 

 diameter, 34.3 mm. ; lesser diameter, 26.1 mm. 



This species differs from 31. poTiderosus (Pfeiffer) in being consid- 

 erably smaller. 



Genus AMPHICYCLOTUS Crosse and Fischer 



1879. AmpMcyclotus Ceosse and Fischer, Journ. Conchyl., vol. 27, p. 46. 



Amphicyclotine shells of helicoid outline, with the whorls marked 

 by fine vermiculated sculpture, which extends over spire, base, and 

 umbilical wall. Operculum thin, corneous, with central nucleus, 

 having the outer edge of the turns slightly upturned. 



Type : AmpMcyclotus houcardi ( [Salle] Pfeiffer) . 



Distribution : Southeastern Mexico to northwestern Honduras. 



