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Modern Classification of the Ammonitide. Read before the — 
Winter Meetings of the Cotteswold Naturalists Field Ciub, held at 
the Science School, Gloucester, on the 17th February, and 17th 
March, 1880. By Dr. Toomas Wricut, F.R.S., F.G.S. 
The essential characters on which Von Bucy and D’Orsieny 
based their Ammonite groups were derived—Ist, from the 
greater or lesser complication in the ramifications of the 
suture-line, and the character of the lobes and saddles formed 
therefrom; 2nd, the position and structure of the siphuncle ; 
and 3rd, the form of the spiral of the shell. 
The first character Von Bucu considered of primary import- 
ance, and on this alone proposed the families, as he called 
them, in his classical memoir, ‘“‘ Die Ammoniten in den dlteren 
Gibirgs-Schichten, 1830.” Subsequent observations, however, 
made by many independent students have taught them that this 
character, although an important one, is not so stable as the 
great naturalist believed—a fact which we have ascertained 
by noting the changes from simplicity to complexity in the 
morphology of Goniatites, Ceratites, and Ammonites. In adult 
life, however, the form of the suture-line is a valuable character, 
and ought to be accurately drawn from careful tracings made 
on the specimens themselves over the natural lines, and not 
given as mere sketches by the artist, as is often the case; 
in tracing the lines we have a natural impress, by the other 
mode a mere ideal representation; so that, whenever suture- 
lines are exposed and can be traced on the specimen, they 
should be carefully noted and recorded. 
In all the Ammoniripz the position of the siphuncle is 
invariably in the centre of the abdomen, and in the outer 
margin of the greater curvature of the spiral of the shell, 
opposite to the columella or dorsal border, the presence or 
absence of a keel in which it is sometimes lodged, and the 
roundness or flatness of the siphonal or abdominal areas, all 
afford specific characters which it is important to note. 
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