187 
forms which have been detached from other genera owing to 
the discovery of new characters in these special forms; and 
Dr. Waacen has proposed the genus Peltoceras in his work on 
the Cephalopoda of the Jura of Kutch, for certain forms which 
he has described in his great work on the Indian Jurassic 
Ammonitide. As new discoveries are made in the structure 
of these Polythalamous shells many errors will be corrected, 
omissions supplied, and new genera erected for the reception 
of the corrected types of this wonderful assemblage of Cepha- 
lopoda which have been collected from the secondary formations 
(Mesozoic rocks) of Europe, and from beds of the same age in 
Asia. The Cephalopoda of the Cretaceous rocks of Southern 
India have been admirably figured and described, Belemnitide 
.and Nautilide by Henry F. Buanrorp, Hsq., F.R.S.; Ammon- 
tide, with revision of the Nautilide, by the late Dr. Frrp. 
Sroniczka ; the Jurassic Fauna of Kutch, the Cephalopoda 
Belemnitide Nautilide, and Ammonitide by Dr. W. Waacen. 
All these works are contained in the Palcontologia Indica, part 
of the Memoirs of the Geological Survey of India. 
Professor AtpHrus Hyarr published in the Bulletin* of the 
Musewm of Comparative Zoology, Harvard College, Cambridge, 
Mass., U.S., a memoir on the Fossil Cephalopods of the Lias 
contained in the Museum of that College, in which he gave an 
outline of anew classification and nomenclature of these fossils. 
He states that the Ammonoids, including all the Cephalopods 
with serrated or foliated septa, the Clymenie, Goniatitis, Ceratites 
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 considered 
some of these groups as natural families, and deemed them 
capable of a division into subordinate groups of generic 
importance. He imparted this fundamental idea to Professor 
Hyarr, at the beginning of his studies on these interesting 
fossils, and selected the five genera which are referred to his 
authority as examples of the manner in which the subject 
* “Bulletin of the Museum of Comparative Zoology, Harvard College, ° 
Cambridge, Mass., vol. i. No. 5, p. 71. 1866. 
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