42 The MoUuscan Family Planorbidae 



Woodward, 1926; Pilsbry and Bequaert, 1927; F. C. Baker, 1928; Haas, 

 1929; Lindholm, 1926; thiele, 1931; and others). Germain (1931), in his 

 Mollusks of France, recognized five families, the four previously alluded 

 to and Bulinidae, the groups of which were thought to constitute a family. 

 Many other works might be listed, especially by European writers, as 

 Lindholm, Westerlund, Clessin, Dybowski, Odhner, Pallery, Preston, Soos, 

 and others. The most important of these are listed in the synonymy under 

 the different genera. The large monographs, such as Clessin ( 1886) and 

 Sowerby (Reeve, 1872), do not help much in family distinctions and the 

 lesser faunal lists of both continents, of which there are many, simply copy 

 the classification as published in some of the works mentioned above. 



In the matter of generic distinctions among the planorbids there is 

 little of note in the earlier works. In 1884, Tryon listed most of the group 

 names as subgenera of Planorbis, recognizing Segmentina as a distinct 

 genus. Pompholyx, Carinifex, and Choanomphalus are listed as genera with 

 some subgenera, mostly fossil groups. In 1905, Dall considered all groups 

 but Segmenti7Ui as subgenera of Planorbis. Germain, 1921, followed Dall. 

 Kennard and Woodward (1926) did likewise. In 1926, F. C. Baker recog- 

 nized the groups Helisoma, Planorbula, Menetus, and Gyraulus as being of 

 generic rank and in 1928 fully described these groups, giving anatomical 

 reasons for their distinction. Among European works, Lindholm in 1926 

 recognized as of generic rank Planorbis, Tropidiscus, Spiralina, Anisus, 

 Gyraulus, Bathyomphalus, Armiger, Hippeutis, and Segmentina, a great 

 step in advancement over previous works as regards classification. Thiele 

 in his Handbuch (1931) was too conservative, listing all groups as sections 

 under the genera Planorbis and Anisus. Mori (1938) in his classification 

 of Japanese Planorbidae followed Thiele. It is to be observed, however, 

 that all of these genera or subgenera as treated by early authors, were 

 diagnosed from shell characters for the most part. 



In a review of the classifications of the Basommatophorous grouji the 

 change in number of families and genera recognized is noteworthy. From 

 one family in 1870 (Limnaeidae or Physidae) this grouping has grown 

 to five at the present time, indicating a tendency to recognize smaller 

 group differences and also indicating advance in knowledge concerning 

 these groups. Many generic and subgeneric names have been proposed 

 during the past ninety or one hundred years but these were founded almost 

 wholly on shell characteristics. No such analytical studies as those on 

 the land mollusks by H. A. Pilsbrv and bv H. B. Baker were made until 

 after the year 1920. 



Studies of the anatomy of the Planorbidae began in Europe many years 

 ago but were confined to only a few species. ]\Iost of the early papers or 

 works on anatomy simply gave as illustration a familiar example, as, 

 for example, Planorbis corneus and Limnaea stagnalis figured by Moquin- 

 Tandon in 1855. Baudelot (1863) published good figures of the genitalia 

 and other organs of Planorbis corneus {= Planorbarius) . In 1867, Ficinus, 

 an almost forgotten WTiter, published an article on the penis of Planorbidae 

 in which he divided the European species of Planorbis into two groups, 

 (1) with a penial stylet, including Planorbis vortex, leucostoma, spirorbis, 

 albus, and contortus, and (2) without a stylet, including Planorbis corneus, 

 nitidus, and Jontanus. He erected the genus Appendicularia for Planorbis 



