12 INFERIOR OOLITE AMMONITES. 



South of England, either in situ or separate. This is very much to be wondered 

 at and regretted, as there is little doubt that a knowledge of the Aptychus would 

 give us help and information in the matter of subdivision. 



I commence this Monograph with the study of the Falciferi or part of the genus 

 Harpoceras of Waagen, and I here give a short account of the history and origin 

 of some of the principal genera. 



It was in 1867 that Alpheus Hyatt published in the c Bulletin of the Museum 

 of Comparative Zoology at Harvard College,' in Cambridge, U.S.A., a comprehen- 

 sive system of families and genera for the Ammonites contained in that Museum. 

 Unfortunately, however, his paper is unaccompanied by any plates, and his 

 descriptions are rather short and terse, the paper chiefly being made up of refer- 

 ences to various authors and to the localities whence the specimens came. 



Hyatt does not seem to have dealt with anything besides Ammonites from the 

 Lias, to which formation almost all his genera belong, only one species in his paper 

 being from the Inferior Oolite proper, namely, Lioceras concavum, although Lioceras 

 opalinum, Grammoceras radians, &c, may be said to belong to it. This paper, 

 however, is most important to us in the study of the Inferior Oolite Ammonites. 

 It enables us to assign, if possible, the correct generic appellations to the 

 various species, because it was one of the early efforts made towards a very 

 complete subdivision of the genus "Ammonites," and because Hyatt went so much 

 farther in that direction than his contemporaries. Let us now examine a few of 

 his genera, and, as one in which we shall be soon interested, let us take Lioceras 

 In this genus Hyatt seems both to myself and others to have united several very 

 different groups of species. For instance, Haug, 1 who has written a capital 

 pamphlet on the Harpoceratidse, has retained under the subgenus Lioceras, 

 L. concavum, L. opalinum, L. elegans of Hyatt's paper, but he has placed Am. 

 lythensis in a group of its own and Am. discoides in the group of Am. falcifer. 

 We must, therefore, as Hyatt has not given us a species as his type of the genus, 

 take the larger number which evidently comprise one group, and we conse- 

 quently select Lioceras opalinum as the type, followed by Lioceras elegans, &c. 

 It may be objected that, as Hyatt placed Am. lythensis first, he intended it for his 

 type ; but the Opalinum group are in a majority, and have been usually taken 

 as the types of Lioceras to the exclusion of other forms. We wish, therefore, 

 to amend Hyatt's genus by restricting it to the group of which Lioceras opalinum 

 is the type. 



As to the genus Grammoceras, which also contains species of diverse character, 

 Grammoceras striatulum seems to be usually taken as the type with Gram, radians^ 

 Am. aalensis and Am. costula undoubtedly form a distinct group, while Am. 



1 E. Haug, " Beitrage zu einer Monograpbie der Ammoniten-Gattung Harpoceras," ' Neuea 

 Jabrbuch fiir Mineralogie, &c.,' Beil.-Bd. iii. 



