THE CYCIiOPHORID LAJMD M0LLUSK9 OF AMEIRIOA 173 



The type, U.S.N.M. No. 198079 was collected by Dr. Edward 

 Palmer at Gomez Farias, Tamaulipas, Mexico. It has 5.6 whorls 

 and measures : Height, 14.4 mm. ; greater diameter, 25.2 mm. ; lesser 

 diameter, 18.5 mm. 



The soluteness of the whorl a little distance behind the edge of 

 the peristome and the exceedingly deeply incised tear-shaped sinus 

 on the parietal wall readily distinguish this species from the other 

 members of the genus that do not have a thread in the suture. 



CYRTOTOMA MEXICANUM (Menke) 



Plate 22, Figubes 4-6 



1830. Cyclostoma mexicanum Mexke, Synopsis methodica molluscorum, p. 133. 



1847. Aperostoma mexicanum Troschei., Zeitschr. Malak., vol. 4, p. 44. 



1850. Cyclotus mexicanus Gray, Nomenclature of molluscous animals and shells 



in the collection of the British Museum, pt. 1, p. 9. 

 1852. Cyrtotoma mexicanum Morch, Catalogus conchyliorum . . . Comes de 



Yoldi, vol. 1, p. 40. 

 1864. Cyclotus mexicanus Binney, Bibliography of North American conchology, 



pt. 2, p. 122. 

 1878. Aperostoma (Cyrtotoma) mexicanum Nevill, Hand-list of Mollusca in 



the Indian Museum, vol. 1, p. 258. 

 1886. Halropoma mexicanum Fischer and Crosse, Mission scientifique au 



Mexique et dans I'Am^rique centrale, vol. 2, pt. 7, p. 130, in part. 

 1890. Cyclophorus (Cyrtotoma) mexicanus von Martens, Biologia Centrali- 

 Americana, p. 7. 

 Shell depressed-helicoid, covered with a straw-colored periostra- 

 cum. Nuclear whorls almost 2, small, well rounded. Postnuclear 

 whorls well rounded, marked by rather rough, retractively slanting, 

 somewhat irregular, rather strongly raised axial riblets. Suture 

 deeply impressed. Periphery well rounded. Base well rounded, 

 marked by the continuation of the axial ribs, which pass undimin- 

 ished over the umbilical wall. Umbilicus broad. The last whorl 

 is solute for about one-tenth of a turn; the auricular portion of 

 the peristome, however, is attached to the preceding turn. Aper- 

 ture subcircular; peristome rather broadly expanded and reflected. 

 The parietal wall bears a deep U-shaped notch. 



The specimen described and figured, U.S.N.M. No. 321058, comes 

 from Veracruz, Mexico. It has 5.8 whorls and measures: Height, 

 15 mm.; greater diameter, 23.6 mm.; lesser diameter, 16.6 mm. 



U.S.N.M. No. 321024 contains another specimen from Veracruz, 

 and there are two additional lots from Mexico without specific lo- 

 cality in the collection of the National Museum. 



This species differs from C. goUmani in having the peristome 

 much more broadly expanded. 



428349—42 12 



