86 



MANUAL OF THE MOLLUSCA. 



for having taking in all their tentacles, they upset their boat, and so return to 

 the bottom." 





Fig. 44. Nautilus expanded.* 



Distr., 2 or 4 sp. Chinese seas, Indian ocean, Persian gulf. 



Fossil, about 100 sp. In all strata, S. and N. America (Chile). Europe, 

 India (Pondicherry). 



Sub-genus. Aturia (Bronn), = Megasiphonia D'Orb. 



Type, N. zic-zac Sby. PL II., fig. 12, London clay, Highgate. 



Shell, sutures, with a deep lateral lobe ; siphuncle nearly internal, large, 

 continuous, resembling a succession of funnels. 



Fossil, 4 sp. Eocene, N. America, Europe, India. 



Sul-genus ? Discites, McCoy. Whirls all exposed ; the last chamber 

 sometimes produced. L. silurian. Garb : limestone. 



Temnocheilus, McCoy. Founded on the carinated sp. of the Carb. lime- 

 stone. 



Cryptoceras, D'Orb. Founded on N. dorsaMs Phil, and one other spe 

 in which the siphuncle is nearly external. 



* Ideal representation of the nautilus, when expanded, by Professor Loven, 

 appears to have taken the details from M. Valenciennes memoir in the Archives dn 

 Museum, vol. 2, p. 257. //,, hood, s, s : phon. It is just possible, that when the 

 nautilus issues from its shell, the gas contained in the last, incomplete, air-chamber, 

 may expand ; but this could not happen under any great pressure of water. 



