32 University of Michigan 



Part II. Operculates 



HELICINIDAE^ 



Oligyra {Snccincta) ftavida streheli (Pfeiffer). 



H. flavida Menke (1829). The usually larger, more southern, 



banded form. 

 H. trossula Morelet (1849). A synonym of the preceding. 

 H. hrevilabris Pfeiffer (1857). From description, a still larger 



form. 

 H. strebeli Pfeiffer (1861). Usually smaller, thinner and more 



depressed, with 5 to S/^ whorls; used here as subspecies. 



About 800 adults ; from leaves of trees, shrubs and vines 

 (H, I, b), and on the ground (H, I, a) in the lowland forest; 

 dead shells from the burnt-over area (H, II, a) ; from leaves 

 of shrubs, cacti, etc., in the savannah forests (H, III, m) ; and 

 from shrubs and elephant-ears along Arroyo Hueyapam (H, 

 II, b). . 



None of the specimens are banded, but the ground-color 

 varies from vitreous white and milky white, through horn- 

 colored and greenish horn-colored, to yellow and dark amber- 

 brown. The last two color-forms are especially striking. The 

 lip is always milky white. Extremes measure : 



Altitude Greatest diameter Height aperture Diameter aperture 



6.1 mm. 93 (5.7 mm.) 48 (2.9 mm.) 52 (3.2 mm.) 



4.5mm. i02(4.6mm.) 53 (2.4mm.) 58(2.6mm.)2 



The spiral striations in these specimens are very variable ; 

 they may be quite well developed or almost completely absent. 



^ The radulae of the four species included here have been exam- 

 ined and are figured in another paper, "Notes on the Radula of the 

 Helicinidae," which will appear in the Pi'oc. Acad. Nat. Set. of Pliil- 

 adcIpJiia. As the synonymy of the North American mainland species 

 is also treated in that paper, it is omitted here, except where it is 

 actually discussed. 



2 Throughout this paper, the altitude is expressed in millimeters, 

 but the other dimensions are expressed as indices. The index of each 

 dimension is taken as that dimension divided by the altitude. The 

 index is followed by the actual dimension in millimeters. 



