44(3 UNITED STATES GEOLOGICAL SURVEY OF THE TERRITORIES. 



not believe them strictly congeneric with Ammonites as properly restricted ; 

 though their types are necessarily, in part, included in the citations I have 

 made. The exception to which allusion is made above, is Coronoceras, 

 which, according to the most generally accepted rules of nomenclature, I 

 regard as an exact synonym of Ammonites as restricted by Lamarck's cited 

 example in 1801. This will be more clearly understood by the following 

 history of this genus, as formerly understood. 



The name Ammonites was, I believe, first used by Breynius in 1732; 

 but as he dates before the commencement of the binomial system, and 

 therefore did not use the words genus and species in the Linnaean sense, I do 

 not think that he can be properly regarded as the founder of the genus. It 

 was also subsequently adopted by Wallerius, Martini, Linnaeus, Gmelin, and 

 others, but not in a binomial sense as the name of a genus. Even Linnaeus 

 and Gmelin, after the introduction of the binomial system, merely used it as 

 a kind of specific term, under the name Helmintholithus, which was made to 

 include fossils of many kinds. Consequently, it is to Bruguiere, in 1789, 

 that we have to come as the founder of the name Ammonites, in a binomial 

 sense, as the name of a genus. He, however, included species belonging to 

 several genera, according to the prevalent classification of such shells at this 

 time, without stating what species he regarded as the type of the genus. 

 This left it for some of his successors to select, from his included species, 

 the one to be regarded as the typical representative form of the genus. 

 Lamarck, who was the first to follow him in the use of the name, in his 

 I'rodr., 1799, cited no particular species by name at that date ; but two 

 years later, in his little Syst. An., 1801, he again adopts the name, with the 

 same diagnosis, and cites as his only example of the genus, A. bisulcatiis, 

 Bruguiere. Consequently, I should certainly think that this citation fixes 

 that species as the typical form of the genus ; and that the name Ammonites 

 should be retained for the group to which A. bisukatus belongs, however the 

 original genus may be divided or subdivided. For these reasons, it seems to 

 me that Coronoceras becomes an exact synonym of Ammonites as restricted 

 to typical forms. 



In its original comprehensive sense, this genus dates back to the Trias, 

 and ranges through all succeeding formations to the top of the Cretaceous. 

 As restricted, however, to what I regard as the typical group, it is probably 

 confined to the Lias. In the latter sense, of course, none of the Cretaceous 



