PI>ATE II. 



Fi(i. 2. — View of tlu' dorsal fiide of a Nautilus i'imhoxciI frouj its slifll. 

 CR, crescentic ridge on the luisterior face of ilu- liodd. 

 DA, dorsal aponeurotic band. 

 DM, dorsal portion of mantle. The index line jioints tn a de|ir(ssion in the dor.-^al side of the hody into 



which tits the involution of tlu' shell. 

 DT', second di<j:ital tentacle. 

 I''., eye. 

 IIoA, auricle of hood. 



lloC. lIoC, eirri of tentacles < iposinir the hooil. 



< )'. |ireocnlar tentacle. 



Si, liase of siphunele. 



\, liacl<wardly projei'tin.n point of dorsal aponeurotic hand, which is evidently the cause of the small liack- 



ward projections near the din>al ed^'es of the .septa, show n in l''ii; I. 

 y, constriction of the sijihuncle w here it jiasses throULdi a septum. 



200 



