2dly. The internal horny or calcareous support, called osselet, and its appendages.[400] ([Lign. 143.])
[400] The bone or shell of the Cuttle-fish, the friable part of which, reduced to powder, forms pounce, is the osselet of that cephalopod.
3dly. The ink-bladder, with its inspissated contents, termed sepia.
4thly. The mandibles of the mouth, or beaks, called Rhyncholites. ([Lign. 150], fig. 1.)
5thly. The soft parts of the animal in the state of molluskite; impressions of the head and tentacula, and remains of the clasps or curved hooks of the arms of some species (see Lign. [140] and [145]).
These several parts are generally found separate, but they sometimes occur in their proper relative position, and from such examples the nature of the original may be determined.
The Cephalopoda[401] are divided into two orders, according to the number of their organs of respiration, or gills; namely, the Dibranchiata, or those which have two gills, (called also Acetabulifera, from their arms being furnished with rows of little cups or suckers;) and the Tetrabranchiata, which have four gills, or branchiæ, and very numerous arms without suckers.
[401] The best systematic account of the Cephalopoda and Gasteropoda, both recent and fossil, yet published, is contained in the first part of the very valuable Manual of Mollusca, by Mr. S. P. Woodward, of the British Museum.
FOSSIL DIBRANCHIATE CEPHALOPODA.