82. 



Pericyclu 



^ f'unatus. 



83. 



,, 



fasciculatus. 



84. 



,, 



Doohvlensis. 



85. 



„ 



multicostatus. 



86. 



,, 



Foordi. 



87. 



„ 



subplicatilis. 



218 CARBONIFEROUS CEPHALOPODA OF IRELAND. 



suture-line — peripheral lobe l deep and undivided, peripheral saddles 2 rounded ; 

 lateral lobes narrow and deep, lateral saddles broadly rounded. 

 Upper Devonian and Carboniferous. 



80. Brancoceras ornatissimum. 81. Brancoceras Enniskillenense.* 



Genus Pericyclus (Mojsisovics, 1882, emend. Hyatt, 1883). — Shell involute, sub- 

 globose to compressed, narrowly to widely umbilicated ; surface of test with strong, 

 direct, transverse ribs, forming a shallow sinus on the periphery, but usually without 

 any sinuosity on the sides of the shell ; constrictions present in some species ; suture- 

 line — peripheral lobe divided by a small median saddle ; 3 peripheral saddles broadly 

 rounded or spatulate ; lateral lobes pointed, deep ; lateral saddles broadly rounded, 

 or forming a shallow arch ; usually with a small auxiliary lobe at the umbilicus. 



Carboniferous. 



88. Pericyclus trapezoidalis. 



89. „ Bailyi. 



90. ,, rotuliformis. 



91. „ plicatilis. 



92. „ Clanensis. 



93. ,, Leesoni. 



Genus Glyhiioceims (Hyatt, 1883, emend. J. Perrin Smith, 1897).— Shell 

 involute, globose to compressed ; "umbilicus usually narrow or closed; periphery 

 strongly convex to subacute ; surface of test smooth or finely striated, often with 

 periodic constrictions; suture-line — peripheral lobe divided by a small median 

 saddle ; peripheral saddles narrow, rounded or pointed ; lateral lobes acute or sub- 

 acute, deep ; lateral saddles broadly rounded or obtusely angular ; usually with a 

 small auxiliary lobe at the margin of the umbilicus. 



Carboniferous and Permo-Carboniferous. 



Sub-genus Sphenoceras, 4 sub-gen. nov. ( = Glyphioceras, Section I [pars], of 

 Hyatt). — Shell involute, globose, with narrow or closed umbilicus, the whorl semi- 

 lunate in section ; surface of test longitudinally or spirally striated, with periodic 

 constrictions ; suture-line — peripheral lobe with a prominent median saddle dividing 

 it into two acute terminations ; peripheral saddles inclined towards the umbilicus, 

 often acute ; lateral lobes acute or very narrowly rounded ; lateral saddles broadly 

 rounded, sometimes with a subacute apex. 



94. Sphenoceras sphsericum. 95. Sphenoceras crenistria. 96. Sphenoceras striatum. 



1 Known also by the names " outer," " external," and " ventral " lobe. 



2 Known also as the " lateral " saddle or " first lateral " saddle. 



3 Called also the " siphonal " saddle. 



1 Referring to the wedge-shaped peripheral saddles and lateral lobes. 



