232 THE LIAS AMMONITES. 



F. Blanford, Esq., F.R.S. ; AnmionitidcB, with revision of the Nautilidcs, &c., by the late 

 Dr. Eerd. Stoliczka ; and the Jurassic Fauna of Kutch, BelemnitidcR, Nautilidce, and 

 Ammonitidds, by Dr. W. Waagen. All these works are contained in the Palceontologia 

 Indica, and form part of the Memoirs of the Geological Survey of India. 



I beg to return my best thanks to H. B. Medlicott, Esq., F.R.S. , Director of the 

 Geological Survey of India, for a copy of these valuable works so useful to me at 

 present, and most important to all Students of Palseontology. 



Professor Alpheus Hyatt published in the Bulletin^ of the Museum of Comparative 

 Zoology, Harvard College, Cambridge, Mass., U. S., a remarkable memoir on the Fossil 

 Cephalopods contained in the Museum of that College, in which he gave an outline of a 

 new classification and nomenclature of these fossils. He states that the Ammonoids 

 including all the Cephalopods with serrated or foliated septa, the Clymenice, Goniatites, 

 Cerafites, and Ammonites proper, were separated by the late Professor L. Agassiz from 

 the Nautiloids and'Dibranchiate Cephalopods, as a distinct order. For many years past 

 Agassiz had considered some of these groups as natural families, and deemed them capable 

 of a division into subordinate groups of generic importance. He imparted this funda- 

 mental idea to Professor Hyatt, at the beginning of Hyatt's studies on these interesting 

 fossils, and selected the five genera which are referred to his authority {Arnioceras, 

 Discoceras, BJiacoceras, &c.) as examples of the manner in which the subject should be 

 treated at the time the investigation was recommended to his pupil. 



The materials in possession of the Museum were all derived from typical European 

 collections, as those of Professors Bronn and de Koninck, MM. Boucault and Duval, 

 the late Dr. Krantz, and the Museum of Stuttgart. 



The position of the female Argonauta in its shelly case, says Prof. Hyatt, and of the 

 ISmdilus in its shell, show conclusively that the periphery of the whorls of an Ammonite 

 is the abdominal side, as stated by Professors Owen and Pictet. This view, therefore, is 

 adopted, and the outer side of the whorl is called the " abdominal," and the inner the 

 " dorsal " side, in accordance with their opinion. 



The Lower Lias Ammonites are distributed into four families — Psiloceratid^e 



DlSCOCERATID^, LiPAROCERATIDiE, DeROCERATID^. 



The Middle Lias forms are grouped into seven families — Liparoceratid^, 

 Deroceratid^, Thtsanoid^, DACTTLOiDiE, PhymatoiDjE, Amaltheoid^, Cyclo- 



CEEATIDiE. 



The Upper Lias species are distributed into the following six families : — Disco- 

 CERATID^, Deroceratid^, DactyloiDjE, Thysanoid^, Phymatoid^, Hildoceratid^. 



In the following analysis of this memoir I shall select the most typical examples of 

 each genus under the name they will be described in this Monograph. 



^ 'Bulletin of the Museum of Comparative Zoology, Harvard College, Cambridge, Mass.,' vol. i, 

 No. 5, p. 71 (No. 5 bears no date, but No. 4 is dated June, 1865, and No. 6 is dated December 26th, 1867). 



