Occasional Papers of the Museum of Zoology 5 



*'In the drawing of Camptoceras I sent to you before (tig. 

 4) to show the position of the eye, the bulge behind the left 

 tentacle is not the eye, but a mystery to me. It has no con- 

 nection with the eye, but has some connection with the repro- 

 ductive organs." 



It is evident from these figures that Camptoceras does not 

 belong to the Physidje. The essential characters of the radula 

 with its bicuspid central and the jaw with its accessory plates 

 show quite conclusively that it belongs to the Planorbidse and 

 should probably be placed near to Isidora. The lack of pec- 

 tinate or serriform marginals which are present in that genus 

 according to Jickeli (Fauna N.-O.-Afrika, 1874, pp. 194 ct 

 seq.), Cooke (P. Z. S., 1889, 136), von^ Martens (S. und 

 B. Moll. Ind. Arch., 1897, p. 8), and Sarasin (Sussw. AIoll. 

 Celebes, 1898, p. 19), separate it radically from that group. 

 Standing alone, the radula is not unlike that of some of 

 the Ancylidse, but the shape of the shell and the character of 

 the jaw prevents any association with any of the groups in 

 that family having a somewhat similar radula. The fact that 

 Lanx, usually included in the Ancylidse, has a similar jaw 

 should be mentioned, but that genus has the serrate marginals 

 characteristic of the Lymnaeidae and quite probably should be 

 entirely removed from the Ancylidas. 



