XIII. 



DESCRIPTIONS OF NEW SPECIES 

 AND NEW VARIETIES 



AS EXPLAINED in the foreword, the following technical descriptions 

 AA of new species and new varieties were edited from longhand notes 

 -*- ■*- prepared by Mr. Baker. During the past quarter of a century he 

 examined every important collection of Planorbidae housed in the museums 

 of America and received extensive field collections from many private 

 collectors as well. In the handling of this huge quantity of material he 

 came to recognize fundamental likenesses and differences at vaiying levels. 

 In addition to his study of the shells, his intensive work on the morj^hology 

 of the snails gave him a broad background for the recognition of natural 

 groups. On the one side, he expressed his conclusions in the broad new 

 classification of the Planorbidae as set forth in Part I of this volume. 

 There he evaluated the characteristics on which families, subfamilies, 

 genera, and subgenera may be recognized with safety. On the other side, his 

 attention to the limits of individual variation in characteristics of the 

 shell furnished the basis for the detailed recognition of specific and varietal 

 boundaries. The descriptions of new forms and the redescription of all 

 known species were to have been the final goal of Part II of this study. 



From his incomplete notes the following descriptions include only those 

 for which he had prepared tentative definitions. On other species and 

 varieties, which he obviously thought of as new, he had not committed 

 himself through the preparation of manuscript notes and in the assembly 

 of illustrations. 



The descriptions of nine new species and seventeen new varieties are 

 arranged in the same sequence of genera and subgenera as outlined in 

 Part I (see pages xiv and xv of the Contents) . 



All tabular arrangements of shell measurements are expressed in 

 millimeters. 



GENUS Tropicorhis 



Tropicorhis shivtieki, New Species 



Plate 134, figs. 12-14, 28 



Shell solid, small, of three and one-half whorls. Upper surface showing 

 three and one-half whorls which are subangulate above, sutures very deep. 

 Lower surface showing three and one-half whorls which are subangulate in 

 the middle, sutures very deep. Whorls rounded on the i)eriphery. Apical 

 whorls sunken on both surfaces. Whorl slightly deflected at aperture. 

 Aperture Innately rounded, outer lip thick with callus. A callus on parietal 

 wall connecting the extremities of the outer lip. Sculpture of coarse growth 

 lines with fine spiral lines. Apertural lamellae six, those of sigmoid form 

 extremely short and thick, only slightly more than half the length of those 

 found in obstructus. 



218 



