CLASSIFICATION. 



teeth as characters of all his sub-orders, and introduces into the 

 nomenclature, for the first time, several new names taken from 

 the form of the teeth. Thus the section H. of Loven is called 

 Rhipidoglossa, including the Scutibranchs. that is to say, 

 Neritidse, Trochidse, Haliotidae and Fissurellida 1 . For the sec- 

 tion L. of Loven he proposed the term Toxoglossa. Tsenioglossa 

 corresponds to the Ctenobranchous Gasteropods, having seven 

 rows of teeth (3. 1. 3.), excepting the operculate pnlmonates, 

 although they may have the same form of teeth. Thus Cyclos- 

 toma is placed in another sub-order from Valvata and Paludina. 

 The Heteropods, which have the same general disposition of the 

 teeth as Tsenioglossa, are regarded as an order, with the same 

 value as the Gasteropods an opinion still maintained by this 

 author. 



In 1853, Dr. Gray, in adopting the names of Prof. Troschel, 

 proposed several new groups, according to the form of the teeth.* 



1. Hamiglossa. Three ranges of teeth (1.1.1.), the lateral 

 versatile. This last character appears to Prof. Morch to be con- 

 sequent upon the rupture of the tissues ; it is observed above all 

 when there is abundance of water under the compressor, 



2. Odontoglossa. Including only Fasciolaria, Mitra and Tur- 

 binella, which have the same form of teeth, but of which the 

 laterals are not versatile. 



3. Rachiglossa. A single row of teeth (0. 1. 0.) ; the laterals 

 having disappeared. 



4. Dactyloglossa. Only differing from Taenioglossa by their 

 lateral teeth, which are wider, with very profound comb-like 

 incisions. 



5. Ptenoglossa. Teeth nearly subulate, in numerous longi- 

 itudinal rows ; Scalaria, Acteon. 



6. Gymnoglossa. No teeth : Architectonidse, Acusidse, Can- 

 cellariadse, Pyramidellidse. But teeth have been since discovered 

 in the three first families. There are, doubtless, many genera 

 indubitably deprived of teeeh. without, for that reason, forming 

 separate groups. 



Gray has regarded these different groups as having a sys- 

 tematic value inferior to that of the form of the proboscis. Thus 



Proc. Zool. Soc., 32, 1853. 



