2 University of Michigan 



mersed. funicular; umbilicus narrow, deeply funicular; su- 

 perior and basal carinae each forming a distinct, prominent, 

 rounded cord ; whorls flat, almost straight-sided ; lines of 

 growth strong, revolving sculpture distinct ; aperture large, 

 somewhat descending, auriculate, higher than wide, angled at 

 . the carinae ; lip thickened within, edge sharp, somewhat ex- 

 panded at the outer edge. Altitude, 6.5 mm.; diameter, 11.5 

 mm. ; height of body whorl in front of aperture, 4.8 mm. 



Type Locality : South Arm of Pine Lake, about two miles 

 north of East Jordan, Charlevoix County, Michigan. 



Type Specimen : Aluseum of Zoology, University of Mich- 

 igan, No. 27440. Cotypes in the collection of Bryant Walker. 



This form combines features of at least two other varieties 

 of Planorbis anfrosus, but is typical of none of them. It is 

 perhaps nearer to porfagciisis in size and general appearance, 

 but dififers from that form in having pronounced cords accent- 

 ing the carinae, in flatter whorls, and in the wider angle 

 which the upper edge of the aperture makes with the super- 

 ior carina. It resembles royaleiisis, but dififers from that sub- 

 species in its smaller size, in the relatively smaller size and 

 auriculate shape of the aperture, the two corded carinae, flat- 

 ter whorls, and finer, more regular lines of growth. 



The series shows some variation in the degree of descent 

 of the aperture, resulting in some specimens in the aperture 

 being applied to the lower half only of the body whorl. In 

 twenty adult specimens the altitude varies from 7.5 to 5.8 mm., 

 diameter from 13. i to 11.5 mm., and altitude of the body whorl 

 in front of the aperture from 5.0 to 4.3 mm. 



Ferrissia michiganensis, new species 

 Figs. 6, 7, 8 

 Shell depressed, oval, slightly wider anteriorly, anterior and 

 posterior margins broadly rounded, the latter slightly oblique 



