THE CYCLO'PHORID LAND MOLLUSKS OF AMEEilCiA 203 



Subgenus Neocyclotus Fischer and Crosse 



1886. Neocyclotus Fischer and Ceosse, Mission scientifique au Mexique et dans 



I'Am^rique centrale, vol. 2, pt. 7, p. 148. 

 1910. Neocyclotus Pilsbby, Proc. Acad. Nat. Sci. Philadelphia, 1910, p. 533 



(Cyclostoma dysoni Pfeiffer designated as type). 



Aperostomid mollusks with helicoid, openly umbilicated shell, 

 marked by anastomosing axial sculpture. Aperture with the outer 

 peristome acute, the inner somewhat thickened, and the posterior 

 angle slightly drawn out. Operculum covered on the outside with a 

 thick calcareous deposit, which forms a weak ridge on the inner edge 

 of the whorls and tapers outwardly, its surface being obliquely 

 striated. 



Type: AperostoTTia (Neocyclotus) dysoni (Pfeiffer). 



Distribution : Southeastern Mexico to Colombia. 



A. (N.) dysoni anibiguum (v. Martens) yields the following data: 

 Radula, 3:3:3:2. Jaw without distinct median projection. Penis 

 typically aperostomid, situated on back of neck behind the tentacles 

 with penal groove and short terminal appendage. The mollusk that 

 we refer to as A. {N.) dysoni hinkleyi was said by Crosse and 

 Fischer to have the radula formula 3:3:3:2. 



KEY TO THE SPECIES OF SUBGENUS NEOCYCLOTUS « 



Umbilicus narrow. 



Summit of whorls decidedly flattened wetmorei 



Summit of whorls not decidedly flattened dysoni 



Umbilicus wide. 



Umbilicus rapidly enlarged at last whorl. 



Suture of last whorl deeply channeled corpulentum 



Suture of last whorl not deeply channeled sanctaemarthae 



Umbilicus not rapidly enlarged at last whorl ; regularly increas- 

 ing from apex chrysacme 



APEROSTOMA (NEOCYCLOTUS) WETMOREI, new species 



Plate 41, Figuees 13-15 



Shell subglobular, covered with a dark olivaceous-brown perios- 

 tracum, which is axially irregularly streaked with wood-brown lines. 

 Interior of aperture bluish white, with a livid cast. Nuclear whorls 

 decollated in all our specimens. The postnuclear whorls are strongly 

 rounded and marked by retractively slanting, more or less interrupted 

 axial riblets, which give an almost nodulose aspect to the surface of 

 the shell. The axial elements are separated from the interspaces by 

 a width about equaling them. Suture moderately well constricted. 

 Periphery strongly rounded. Base inflated, strongly rounded, nar- 

 rowly openly umbilicated. The posterior half is marked like the 



3 We have not included A. (N.) smithi Pilsbry and Clapp in this l^ey, as we have not seen 

 specimens of it. 



