Dec. CADOCERATIDJE xiii 



1918 



Genus, FIMBRILYTOCERAS, nov. 

 Type, F. fimbriatum, J. Sowerby sp., Plesiotype (Y.T.A. CXXX b) 



Am. fimbriatus ; d'Orbigny, being taken as genotype of Lytoceras, 

 the series to which Am. fimbriatus, Sowerby, belongs, according to present 

 interpretations, requires a new generic name. 



Lytoceras has persistently a large number of strong, plain, arcuate 

 " flares " (lamelke) " par tour de huit a douze " (d'Orb. 314), the ribs 

 all fimbriate, the fimbria? being represented in his figure as strong, almost 

 pustulose, but " le moule est entierement lisse " (d'Orb.). Present genus 

 shows small flares, straight and radial after the dorsal curve; plain as 

 well as fimbriate ribs — the fimbriae of low relief ; and an ornate cast. 

 On inner whorls, which have test, flares are numerous, small and fimbriate 

 (or sea Hopped), little different from adjacent fimbriate ribs. On outer 

 hall whorl are only two flares (or their indications — constrictions on cast). 

 The plain ribs are more or less connate and alternate with the fimb- 

 riate, and there are occasional short intercalate plain ribs on periphery, 

 extending more or less to sides. 



In PI. CXXX A the original figure of Am. fimbriatus, Sow., is re- 

 produced and a plaster cast of a plasticine impression to show style of 

 ornament— photographs x 2. It has remains of one flare, presumably 

 plain and not very prominent. Owing to the regulations of the Oxford 

 University Museum, photographs of this specimen could not be obtained. 



In PI. CXXX b are reproduced photographs of a topotype, nat. size 

 and enlarged. 



PI. CXXX c illustrates an older example, a topotype, last one-third 

 of body-chamber lacking test. There are many old-age changes— flares 

 have become numerous — four ; and fimbriate ribs are crowded in places, 

 distant in others, obsolescent except on periphery ; longitudinal lineation 

 is acquired, especially on periphery, causing plain ribs to appear in- 

 cipiently fimbriate. 



Family, PACHYCERATID/E, nov. 



Cadicones (more or less coronate) declining to platycones and retaining 

 ribs — smoothness and excentrumbilication later. Genera, Erymnoceras, 

 Pachyceras, Macrocephalites, Tomquistes. Cone-development opposite to 

 that of Cadoceratidae, Hyatt. Possibly connected with Stepheoceratidae 

 in a wide sense, that is, to Bajocian Coronates. 



Family, CADOCERATIDJE, Hyatt, 1900. 



Syn. Cardioceratidae, R. Douville, 1912, pars (H. Douville 1890, not technically 



published ?) 



Costate serpenticones (and platycones) which develop inflation in 

 varying degree, from feeble swelling up to cadicones or sphaerocones ; 

 catagenetic features like loss of ribs and excentrumbilication occur during 

 (or before ?) this stage. In some series venter develops to flatly arched 

 with straight ribs; others show varying degrees of rib angulation along 

 median lines of angulate or arching venter, making more or less of crenulate 

 carina, sometimes very strong — producing almost homceomorphs of 

 P alto pleuroc eras. Some genera finish in inflated stage ; others carry on 

 decline to oxycone, producing in some cases homceomorphs of Amaltheus. 

 Varying degrees of inflation, umbilication, peripheral development, with 

 style of costation and septal development furnish characters for many 

 genera. At present named, Cadoceras, Quenstedtoceras, Chamoussetia, 

 Cardioceras, Amoeboceras : many more required. Possibly connected with 

 Oppelidae. 



