566 MOLLUSCA SUB-KINGDOM VI 
solid broad bifid saddles. The division of these by large secondary lobes is similar to 
that which occurs in the first laterals of Manticoceras and Sporadoceras, but affects more 
of the primitive laterals. Aperture with only short broad crests on the venter. 
Includes only Didymites, Mojs. (Fig. 1166), from the Alpine Trias. 
Family 8. Cladiscitidae. Zittel. Some shells resembling <Arcestidae, but 
typically the sides are flat, venter plano-convex, and surface usually covered with 
longitudinal ridges. Sutures similar to Arcestidae, but more complex, the saddles 
being reduced in many forms to thread-like narrowness. Growth-lines like those of 
Didymites on the sides, but have crests at the ventro-lateral angles, and very broad 
ventral crests. 
Cladiscites (Hypocladiscites), (Fig. 1167) ; Psilocladiscites, Procladiscites, Paracladis- 
cites, Mojs. Trias. 
LV. PHYLLOCERATIDA. 
Shells as a rule with peculiar, prominent bands of growth. Saddles in primi- 
tive genera have the monophyllic bases of those in Popanoceratidae, but in more 
specialised groups the marginal saddles alone retain the same rounded outlines. Dorsal 
saddles and lobes are, as a rule, at least three in number. Antisiphonal lobe often 
bifid and retains either entire outlines on both sides, or with a few simple marginals, 
or has but one partr of short lateral branches. Aperture with well-marked but short 
ventral crest. 
Family 9. Megaphyllitidae. Mojsisovics. Conchs compressed, discoidal, or 
involute. Sutures with primitive monophyllic saddles, and more regular in the 
relative size of the lobes 
and saddles and in their 
marginals than sueceed - 
ing families. Anti- 
siphonal lobe bifid but 
otherwise entire. 
Monophyllites (Fig. 
1168),  Megaphyllites, 
Mojs. (Fig. 1169); 
Mojsvarites, Pompeckj ; 
Discophyllites, gen. nov. 
Type D. (Lytoc.) patens, 
Mojs. sp. Trias. 
Family 10. Us- 
suritidae. Conchs 
compressed, — discoidal, 
Fig. 1169. and involute. Sutures 
A, Megaphyllites imsgetus, have modified mono- 
Mojs. Upper Trias; Sand- 3 Z 
ling, near Aussee, Austria. phyllie first lateral 

Fic. 1168. 
Monophyllites Simonyi, Hauer sp. Upper B, Suture-line of M. Jarbas, 
Miinst. saddles, the second 
laterals more or less 
pointed in Ussuria, Auxiliary series remarkably irregular, and all the lateral lobes 
with very large, more or less pointed, but still phyloidal marginal lobes and saddles. 
Ventral lobe broad and short, and siphonal saddle very large. 
Ussuria, Diener; Ussurites, gen. nov. Type U. (Monophyl.) sichoticus, Diener sp. 
Trias. 
Family 11. Phylloceratidae. Zittel. Principally involute shells with very 
complex sutures, which, however, still retain monophyllic outlines in the marginal 
saddles. Antisiphonal lobe with entire sides, or with only one pair of short lateral 
branches, and extremities usually bifid. 
Trias ; Rothelstein, near Aussee, Austria. 
