CLASS V 



CEPHALOPODA 



651 



The fainily of tlie Phylloceratidae is tlie most persistent and the longest-lived 

 aniong the Amnionoids, being continuoiis from the Permian to the Upper Cretaceous. 



Subfaniily A. Monophyllitinae Smith. 



Sliells compressed, discoidal, evolute. Septa with primitive monopliyllic saddles, 

 and more regulär in the relative size of the lobes and saddles than the succeeding 

 group. Antisiphonal lobe bifid, but otherwise entire. MonophylUtes Mojs. (Figs 

 1245, 1246) {Mojsvarites Pompeckj); Discophijllites Hyatt (type Lytoceras patens Mojs.). 

 Triassic. Discophyllites forms a connecting link with the Phylloceratinae, and might 

 with eqiial propriety have been classed with that group. 



Subfamily B. Phylloceratinae Zittel. 

 Form usually involute. Septa very complex, with the saddles deeply digitate, 



Fio. 1248, 



l'hylloceras heterophyllum (Sowb.). Upper 

 Lias ; Whitby, Yorksliire. 



Fhyüoceras ptychoicum (Quenstedt). Tithonian ; Stranibei^, 

 Moravia. AL, Antisiphonal lobe. 



