DM NOTHOCERAS. I 



Shell nautiloid, slightly involute; -M-pta im little curved, not 

 lobed: 



(hie ^prcics. I'. Silurian. Jin/n-inni. 

 ^. I Jo in, MI. i M. Uarr. I 'I. !7. li.ii". !'.><;. 



QUC HERCOCERAS, H.m. 



shell generally nantiloid. the whorls >omei imc-* separated, or 



even nirlmiate: body-chamber with :i diaphragm perpeiidicnl.-ii 

 to the axis of the shell, the concavity of which i> opposed to 

 that of the last st-ptimi. throwing the aperture on the deeply ex- 

 e:)\:i1e(| <lors;il side of tlie >hell : ^iphilli-le dors;i |. cy lilld I'ieM I. 

 intl:itt'd lu-tween the eh:inilier>. scp:ir:iti'<l from the shell. 



Two species. M iddle Silll 1'i.M 11. Ilnln'iniii; I )e\ < >li i;i II. \n**ti H (''.). 



(iriiiK- LITUITES, Hrcyn. 



Shell pl:uiorl>it'orin. the \\horls close or M-pnrate ; the l:ist 

 chnndiei- producel in ;i straii^lit or out wardly curved lino; lateral 

 iiiai'Liins of the ajK-rtni-e extended and curved towards the inte- 

 rior of the shell, rout ructing the aperture into two distinct 

 orifices. 



Twenty-eight species. Silurian. l^urnj,c : North- America. 



L. SIMPLEX, IJnrr. IM. '.IS, li'. 4 ( .l7. 



Shell with the produced portion very short or wantiiiLi. 

 Seven species. Silurian. Norway ; Bohe IHKI. 



(Ji-nits DISCOCERAS, P.;in;ui<l.'. 



Slu-ll planorl)iforni : produced portion very short o 

 :ipTt!irr Dimple, not font ract ed. 



Three sprcies. M iddle Silurian. liu.**in : firnmini/: \<>riru ,/. 



M. llai-i-ande dt'scriles this ;) s a siil^-niis nnder his neiin> l.itu- 



tlU8; of which no species have Iteell ol)^el'\-ed. hilt which 



be creates by anticipation with tin- diairno>i> : Shell like /.////- 



Hi'.<. lint with a Dimple aperlnre," in orU-r that /'/ in;i\ 



hold the >aine n-latioiisliip to it that < >/>/i /<! '< ).< doe's to l.itu- 

 itesl Tliis is tillint.- up the l< gaps' 1 with a vi-nii-eance. and could 



