MI -i OOBH \>. OORON I' K ERAB. 



(It-lined upon tin second whorl. I' inliil icu^ open ; >ide- e\ | H .-<.!. 

 Abdominal lobe deeper and narrower th:in the lateral I- 

 Superior lateral lobes broad, -hallow. ;in.| lull very little !<>i 



fcthan the inferior lateral. The :mxili:iry lateral lobe- .-ue cunei- 

 form, and incline towards the umbilici^. 



Lower and Upper Lias. 



O. -mm s, d'Orh. T. 111?, li-s. (\\-2. r,i:j. 



DlSOOCEBAS, Alxloinen keeled :ind ch:inneled. Hot h eh:i r:n-_ 

 tei's MIT eonstnnt. :ilt.hoiir|i the clininiels ;ii'e sometimes nc.-irly 

 <>lsolete. 1'ilji' smooth. Genicula- cui'ved fc>r\v;mls. Umbili- 

 ens )piMJ. sides tlnttened. exposed. Alxloinen dei)i'essed. A b- 

 doiniiiMl lobe K-e|) ;ind UMITOW. Superior and interior Intend, 

 narrow and ii'i-e^nlnrly pointed with minor lobes. Superior 

 latei'id cell equally divided. Inferior lateral unequally divided. 

 First auxiliary cell well developed, and nearly as long as the in- 

 ferior lateral. 



Lower Lias. 



I). opiiiDioiDES, d'Orb. T. 107, figs. 607, 608. 



COHOMCKRAS. Keels prominent, constant; channels well 

 defined. I'ilte tuberculated and bent. Umbilicus open. Side-* 

 of the whorls exposed. Pilo? preceded by a line of tubercles in 

 the yonnii, which gradually elongate to form the tuberculated 

 pihe of the adult. Ventral lobe deep and narrow. Lateral lobes 

 unequally divided. Superior lateral cell irregularly divided ; 

 abrupt on the siphoual side; sloping rapidly on the opposite 

 side. Inferior lateral cell exceedingly variable in form, but un- 

 equally divided. 



Lower Lias. 



C.-BISULCATIS, d'Orb. T. in:;, tig. 557. 



A-TF.ROI KI; \>. Kei'l well defined, but varies tVoin prominent 



and narrow to depressed and broad. Channels obseure to deep 



aixl well defined. Pihe smooth, depressed : often bent on the 

 -. and appear in the young as lateral folds or large tubercles. 

 Sides in soim; species not enveloped; in others, covered to fully 

 one-half of their breadth. Ventral lobes very deep. Lateral 

 lobes very shallow. Superior and lirM auxiliary cells short and 



broad. Inferior lateral cell very prominent. 



Lower Lias. 

 A. OBTU81 B, Sowtx T. 1(7. I'm-- HI 1. >l-">. 



