7920 STEPHEOCERATIDM 21 



the very varied morphology of this remarkable family. But a pro- 

 visional analysis of the genera now named may be interesting. Three 

 developmental features are striking — (1) the attainment of inflation : 

 in this some genera are very successful — Cadoceras, Goliathiceras, 

 Eichwaldiceras, and seem to end in it; others are fairly successful, 

 Eboraciceras, Vertumniceras, Vertebriceras — the last passes beyond it 

 back into platycone ; others make little progress, and may be said to 

 fail, Pseudocadoceras, Longczviceras, Bou rkelamberticeras ; the last drops 

 off into oxycone; (2) the attainment of carination : in this Vertebriceras 

 is most successful, especially in combining it with fair success in regard 

 to inflation ; Cardioceras is also successful in regard to carination, less so 

 as regards inflation ; Sagitticeras is remarkable for an attempt at 

 carination which comes so near success and yet fails ; some genera show 

 an attempt abandoned as soon as inflation comes — Eboraciceras, 

 Pavloviceras, Eichwaldiceras ; others are successful because inflation 

 takes place only around umbilicus — Chamoussetia, Korythoceras and, 

 in a feeble degree so far as carination is concerned, Goliathiceras ; others 

 seem to make no attempt — Cadoceras, Pseudocadoceras, Prorsiceras ; 

 (3) the attainment of tuberculate ornament : the Argovian and later 

 genera show this — Cardioceras and Vertebriceras, which have also knotted 

 keels ; Amceboceras and Prionodoceras, which have serrate keels. The 

 early genera do not attain the tuberculate stage ; some of the later 

 genera, for instance Prinonodoceras, not only attain it, but lose it — 

 pass beyond it to the catagenetic stage of smoothness. 



In early genera development takes place from a platycone stage —  

 Cadoceras ; in later genera development starts from an earlier stage — 

 the serpenticone — Vertumniceras, Vertebriceras, Goliathiceras, — the platy- 

 cone stage being skipped ; and it is to be presumed that, in the earlier 

 genera, the serpenticone stage has been skipped or forced into insignifi- 

 cance by tachygenesis of platycone. 



In later genera a secondary platycone (even oxycone) stage is 

 developed after more or less of swollen stage, which also may persist 

 into it, though with declining intensity — Prionodoceras. 



A fuller, tabular, analysis of these and other genera of the 

 Cadoceratid family may be attempted later. 



Family STEPHEOCERATIDM, Buckman, 1898 



Suture-line with tubercle, OV, outside of L 2 , later, on to L 2 and, 

 in some very serpenticonic forms, inside it ; L" feeble, generally surpassed 

 by a highly-developed aux. 1. Suspensive lobe may become highly 

 elaborated and long. The cadicone stage passes into serpenticones, 

 and there are no sphjerocones. 



Genera, Stepkeoceras, Buckman, 1898, Normannites, Munier-Chalmas 

 1892, Stemmatoceras, Teloceras, Skirroceras, Epalxites, Mascke 1907, 

 Masckeites, Buckman, 1920. Some other already-named genera may 

 come here, but that has not been proved. 



The family Pachyceratidse (Y.T.A. II, xiii) is presumably a develop- 

 ment of the early members — cadicones — of this one — whorl-shape of 

 Erymnoceras and tubercle-position are the same. Ground for separation 

 may perhaps be found in the simpler suture-line. 



