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under side or dorsum. The dorsal lobe is not, however, affected 

 to the same extent by senile degeneration, and persists, although 

 narrower in proportion in the centre of the suture, as may be seen 

 in Fig. 17, PI. vii. 



The siphuncle is propioventran in all the stages observed from 

 the ephebic to the anagerontic. 



Remeleceras* n. g. 



This genus, known at present only by one species, is closely allied 

 as regards aspect and the late appearance of a contact furrow to 

 Estonioceras. It differs in having a much deeper furrow, a nephri- 

 tic instead of a digonal or depressed elliptical form of whorl and in 

 the dorsal sutures and .apparently also in the extraordinary form of 

 annular muscle. 



Remeleceras impressum. PI. viii, Figs. 1-8. 



Loc. (?) 



This extraordinary form is described and figured in this 

 memoir on account of its interesting connection with the history of 

 the impressed zone, notwithstanding the absence of any informa- 

 tion with regard to the locality. The side view, Fig. 1, PI. viii,. 

 shows the sutures, which are similar to those of Estonioceras, and 

 the impression of what appears to be the annular muscle at the base 

 of the living chamber is very distinct. This may be seen on the 

 dorsal side, Fig. 3, where the lower line has a deeper and broader 

 depression in the cast reaching across the contact furrow. These 

 two lines of depression depart from each other widely on the ven- 

 tral side, Fig. 2, the outer one forming a broad saddle. They of 

 course correspond to raised ridges on the inner surface of the shell 

 of the living chamber and may have been due to abnormal action 

 in the secretions along the upper and lower borders of the annular 

 muscle. 



The depth of the contact furrow in the full-grown shell near the 

 end of the incomplete living chamber was somewhat greater than is 

 given in Fig. 4, but only a shade deeper, and is also slightly 

 deeper than this beyond the base of this living chamber on the 

 septate part of the volution. In younger stages, shown successively 

 in Figs. 5-7, with their accompanying sections, Figs. 6-S, this 

 furrow diminishes in depth and breadth and almost disappears 



* Dedicated to Rernele, well known for his original observations on fossil Cephalopods 



