§ 34. FOSSIL NAUTILUS. 247 



display the internal structure of the original. I shall defer 

 an explanation of the mechanism of these shells to the sub- 

 sequent lecture, when other genera of the same order will 

 come under our notice. The large splendid species {Nau- 

 tilus imperialis) of which hundreds of specimens have been 

 collected from the cuttings at Highgate Tunnel, and the 

 recent railway excavations, is figured in Sowerby's Mineral 

 Conehology ; a work which contains coloured representa- 

 tions of a great number of the British tertiary shells. I will 

 only particularize a rare and elegant species, discovered by 

 Mr. Wetherell, of Highgate, which is here figured of the 

 natural size. 



Lign. 40.— Nautilus ziczac, from the London clay, Primrose Hill. 



(In the cabinet of Mr. Wetherell.) 

 Fig. 1. Side view. Fig. 2. Front view. 



This shell is remarkable for the peculiar character of the 

 septa or divisions, as expressed in the specific name ; the 

 siphunculus extends along the inner margin. The septa 

 are distinctly seen, in consequence of the external layer of 

 the shell having been destroyed by decomposition. 



34. NUMMULITES : AND OTHER FORAMINIFERA. The 



fossils called Nummulites (from their resemblance to a 

 coin) belong to those extremely minute forms of molluscous 

 animals which are termed Foraminifera, from the shells of 

 most of the genera being perforated all over with openings 

 or foramina. 



