1903.] NATURAL SCIENCES OF PHILADELPHIA. 777 



and tj'pical. The species has not before been reported from this part 

 of Mexico. 



Limnsea desidiosa Say. 



Saltillo, State of Coahuila. The specimens are small, reaching a 

 length of only 7.3 mm., but they seem to me to be typical in all other 

 characters. The species is new to Mexico. 



Limnsea palmeri Dall. 



Biologia Cent. Amer., Moll., p. 377. 

 This species has been removed from the Limnceidce by Dall, Avho 

 refers it to the marine genus Reduzia. 



Planorbis tenuis Dkr. 

 Tlalpam, State of Mexico, and Acaml^aro, State of Guanajuata. 



Planorbis tenuis exaggeratus Marts. 



Lake Patzcuaro, Michoacan. A large series collected by ^Ir. Rhoads 

 shows the characters of this subspecies to be remarkably constant. 

 No P. tenuis were found in the lake. 

 Planorbis liebmanni Dkr. 



Topo Chico, near Monterey, Nuevo Leon. 



ANCYLID^. 

 Ancylus exoentricus Morelet. 



Lake La Prassa, near Uruapam, State of ]\Iichoacan. 



Ancylus papillaris Martens. 



Uruapam, Michoacan; Tlalpam. State of Mexico; Monterey, Nuevo 

 Leon. This gi\-es this well-characterized species a wide distribution. 

 It has heretofore been known onl}- from Rio Ameca, State of Jalisco. 



An Ancylus similar to haldcmani was taken at ]\Ionterey, one speci- 

 men. 



PHYSID^. 

 Physa osoulans Hald. 



Tlalpam, State of Mexico; and in the State of Michoacan at Morelia; 

 Lake La Prassa, near I^ruapam; Lake Cuitseo, near Huingo; also 

 from a hot spring near the same place, and a ditch near Lake Patz- 

 cuaro. Acambaro, State of Guanajuata. 



Physa osoulans rhyssa Pils. 



Proc. Acad. Nat. Sci. Phila., 1S99, p. 401. 

 This form is much smaller than P. o. plicata C. and F. Saltillo, 

 Coahuila, and Topo Chico, near Monterey, N. L. 



