INVERTEBRATE PALEONTOLOGY 551 



definite limits, as- his diagnosis was far from satisfactory, while he included 

 numerous species belonging to a number of widely distinct genera, according 

 to modern classifications, without mentioning any one as the type. In 1774, 

 and again in 1776, Miiller used the name Helix to include nearly as wide a 

 range of types. Cuvier, bowever, in 1798, only ranged three species under 

 it, the first of which was Helix pomatia, Linnauis, the typical form of the 

 genus as here understood ; but as his other two species belong to two dis- 

 tinct genera, according to later classifications (though Albers includes all 

 three of these types as sections of this genus), he can hardly be regarded as 

 having restricted the genus to exact limits, or, in other words, as having 

 settled the question in regard to what particular species is to stand as the 

 type of the genus. In 1799, however, Lamarck adopted this genus in his 

 Prodromus, and cites but the single example Helix nemoralis, Linnaeus; 

 though two years later he again used it with H pomatia as his only example. 



I am not sure of having seen all the works necessary to settle the ques- 

 tion whether or not any other author had used this genus in a way to restrict 

 it to any one properly-limited genus, before Lamarck's citation of H. nemoralis 

 as his typical example in 1799; but if this had not been done, I should 

 think, according to the most generally-accepted rules of nomenclature, that 

 the name Helix ought to adhere to the group including H. nemoralis, which 

 group is now generally known under Montfort's name Aeavus. This change, 

 if it should be made, would therefore require the group here under consider- 

 ation to take the name Pomatia, or some one of the later names cited in the 

 synonymy. Not having at hand all the necessary facilities, however, for 

 tracing out fully the complicated synonymy and history of this genus, of 

 course no such innovation will be proposed here. 



Although this genus is here defined in a restricted sense, it must be 

 confessed that practically, in classifying fossil species in the mutilated and 

 distorted condition in which specimens are usually found, we are often com- 

 pelled to refer to it forms which probably could not be properly included in 

 it as here restricted, and thus we have to give it provisionally wider limits. 



It is not, I believe, positively known that this genus dates back further 

 than the Tertiary epoch, though we may have to refer, at least provisionally 

 to it, forms from beds in the far West that may prove to belong to the 

 Upper Cretaceous. 



