CEPHALOPODA. 



43 



titions oblique, and on the upper side concave ; the last 

 chamber large, and able, probably, to contain 

 the whole of the animal : a central siphuncle. — 

 Above 200 species, of various sizes, fossil. 



Probably the substance of all these shells 

 is, like that of the Nautilus and others, formed 

 of a double shelly layer, of which the outer 

 falls off. Philippi says one has been found 

 ten feet long. O. gigantea is said by Sow- 

 erby to be eight feet in length, the aperture 

 being eight or more inches in diameter, and 

 diminishing!; at the rate of an inch in a foot.* 

 This magnificent species is found in the moun- 

 tain limestone of England and Scotland. Dr. 

 Mantell relates that he picked up a fine 

 fragment of one on the beach at Brighton, 

 probably brought by a vessel as ballast, in- 

 dicating as great a magnitude as the above. 

 The siphuncle is dilated between each par- 

 tition into a globular form. O. cordiformis also has 

 siphuncle, composed of a series of hollow globes." f 



Philippi mentions the following as sub-genera : — Go- 

 nioceras Hall ; Mellea Fisch. and Waldh. ; Endoceras 

 Hall; Cameroceras Conrad; Conoceras Bronn. ; Bac- 

 trites Sandberger. 



Tkociioceras. Barrande. — Shell many-chambered, 

 unsymmetrical, rolled up like the Turrilites in the family 

 Ammonitacea ; the partitions simple, nearly like those of 

 the Nautilus or Orthoccras. — 16 species, fossil. 



A perfect description cannot be given until more speci- 

 mens have been discovered. Woodward says that some 

 of the species arc nearly flat. 



the 



* Mineral Conchology. 



\ Ibid. 



