554 



MOLLUSCA 



SUB-KINGDOM VI 



Margaritas (Fig. 1135), Tropites (Figs. 1092, C, 1100, 1136), (Pamtropites, Ana- 

 tropites, Microtropites), Barrandeites, Silbyllites, Mojs. ; Eutomoceras, Hyatt. Trias. 



Family 9. Haloritidae. Mojsisovics (pars). Shells more globose and more 

 involute in the young than Tropitidae, and as a rule keelless, but having similar 

 volutions in a number of species during later stages. Ornament as a rule simpler than 

 in Tropitidae. Aperture usually with ventral crests, but these are primitive in outline, 

 broad, and in some species scarcely indicated by the lines of growth. 



Halorites (Homerites), Jovites, Parajuvavites, Juvavites (Anatomites, Grriesbach- 

 ites, Dimorphites), Miltites, Sagenites (Trachysagenites), Mojs. Trias. 



Sub-Order E. GLOSSOCAMPYLI. Hyatt 



Primitive species exhibit close resemblance to Prolecanitidae, but differ in the greater 

 number and simpler forms of the tongue-shaped saddles and lobes. Specialised shells have 

 the saddles acute, but still entire and of the same fundamental outlines, while the lobes, 

 become bifid or digitated. Adventitious lobes and saddles are introduced by division of 

 the siphonal saddles, and generally show reminiscence of their primitive ancestral outlines. 

 Siphuncle as in preceding groups, devoid of a calcareous sheath; funnels monochoanitic 

 and short in primitive genera (Pharciceras), but becoming chloiochoanitic in specialised 

 forms. Antisiphonal lobe entire in primitive, but bifid in more specialised shells. 



Two pairs of entire dorsal saddles and one pair of zygous lobes with rounded 

 outlines appear in Sandbergeroceras, but in more involute and specialised genera the 

 dorsal inflections become more numerous ; their outlines remain comparatively simple, 

 however, except in Hedenstroemitidae. There is a general tendency in this sub-order 

 toward the multiplication of lobes and saddles, and these are added at both external 

 and internal ends of the lateral sutures. The lobes and saddles are less differentiated, 

 or are more alike, than in preceding 



groups throughout the entire lateral " A /\ m r\ (\ ,. 



line. The sutures of Pharciceras, fawy\f\J\J \J \J\rr A ^J \j \\\]\JV^^ 

 however, show the presence of large *^ 



internal saddles in some species, indicating 

 derivation from Magnosellaridae. 



Family 1. Pharciceratidae. More 

 or less discoidal shells resembling Anar- 

 jcestes, but having the lobes and saddles like 

 those of Beloceratidae, with, however, 

 simpler and more rounded outlines. No 

 adventitious inflections are developed. 

 Ventral lobe undivided, and antisiphonal 

 lobes entire. Aperture with large hypo- 

 nomic sinus. 



Pharciceras, Sandbergeroceras (Triano- 

 eras), Hyatt (Fig. 1137); Hoeninghausia, 

 Giirich. Devonian. (?) Beneckia, 

 Trias. 



FIG. 1137. 



Suture - line of Sandbergeroceras 

 tuberculoso-costatum, Sandb. Upper 

 Devonian. 



FIG. 1138. 



Lcloceras muWlobatum, Beyr. sp. 

 Devonian ; A<lorf, Westphalia. 



Upper 



Family 2. Beloceratidae. Freeh. Includes only the genus 



Hyatt 



