X. 



GENERA WRONGLY REFERRED 

 TO PLANORBIDAE 



Genus NAUTILINUS Mousson, 1872 

 Type by original designation, Hyalina clymene Shuttleworth 



1872. Nautilinus Mousson, Neue Denksch. Allg. Schweiz. Gesell., XXV, p. 19. Type 



Hyalina clymene Shuttl. As subgenus of Hyalina 

 1921. Nautilinus Thiele, Archiv. fiir Mollusk., LIII, p. 111. Type Hyalina clymene 



Shuttl. Radula and generic position 

 1931. Nautilinus Thiele, Handbuch, Teil 2, p. 481. Type A. (N.) clymene (Shuttl.). 



As subgenus of Anisus 



This genus, based on a supposed land snail from Garachico, Tencrife, 

 Canary Islands, is scarcely a member of the family Planorbidae, although 

 so considered by Thiele. The figures given by Mousson (his plate 1, 

 figs. 28-30, natural size, figs. 31-33 enlarged) do resemble some forms of 

 Gyraidus. The shell is very small, only 2 nun. in diameter. Tryon (in Man. 

 Conch., II, p. 172, 1886) places it in Zonitidae and says 'Its habitat is 

 different from the Hyalininae generally, living in wet moss, associated with 

 Physa, Ancylus, and Hydrocena, etc' Pilsbry (Man. Conch. IX, p. 24) 

 lists it among the land shells. Wollaston (1878, p. 324) says 'I am ex- 

 tremely doubtful whether this curious little Planorbis-likc shell should be 

 associated with Hyalina.^ 



In 1921 (p. Ill), Thiele extracted a dried radula from a shell of this 

 species and briefly described the teeth. The formula is 20-1-20. The center 

 tooth is small and has one indistinct cusp. The side teeth (laterals and 

 marginals) have four sharp ctisps. The single cusp of the center tooth re- 

 moves clymene from the Planorbidae in which the center tooth always has 

 two cusps. The form of the shell is distinctly unlike any form of the family 

 Lymnaeidae, in which the center tooth of the radula is imicuspid. The 

 radula resembles some groups of Ancylidae and Nautilinus might prove to 

 be related to this family, perhaps in a similar manner to the American 

 genus Neoplanorbis Pilsbry, in which the shell is particularly Planorbis- 

 like. Only an examination of the anatomy of the animal, especially the 

 genitalia, will definitely settle the question of the taxonomic position of 

 Nautilinus. 



Genus PALAEORBIS Beneden and Coemans, 1867 



1867. Palacorbis Beneden and Coemans, Bull. Acad. Belgique, ser. ii, XXII, pp. 385, 

 390 



The only recent reference to this group, so far as known to the writer, 

 is in Zittel's Grundziige der Palaontologie (Palaozoologie) , Abth. I, In- 

 vertebrata, p. 424, w^iere the following comment is made: 'Hierhcr diirfte 

 wohl auch die Planorhis sehr ahnliche Gattung; die zierliche Palaeorbis 

 Bened. et Coemans em. Reis aus oberkarbonischen und permischen Ab- 

 lagerungen von Europa und Nordamerika gehoren.' The name does not 

 occur in any other edition of Zittel's work. 



The group is believed to include fossil Vermes, possibly Polychaetes. It 

 does not appear to be referable to any mollusk, centainly not to the Pla- 



202 



