﻿BRITISH FOSSIL CEPHALOPODA. 9 



surrounding the jaws, and tough and membranous at the end. The inner layer of 

 the lip is reflected over the mandibles and unites above with the outer layers ; it has 

 longitudinal internal, and circular external, muscular fibres. 



The jaws are somewhat like the beak of a parrot, but not so much so as in the 

 Dibranchiates. The upper one (fig. 3, a) fits into the lower (fig. 3, b), which 

 surrounds it when the jaw is closed. The first has a flat surface inside, and on the 

 outside a nearly flat surface facing outwards and forwards ; the junction of the two 

 being slightly bent inwards to a sharp point. It is divided into inner and outer 

 (and shorter) horny laminae, which separate in passing from the tip and are lost 

 among the muscles. The lower beak is more convex, and bent in at its point, where 

 it is dentated (fig. 3, b) ; it is also produced into two laminae behind, whereof 

 the inner one is the shortest. They are both covered near the tips by calcareous 

 deposits, both inside and outside. 



Within the jaws are found the organs of taste, the odontophore and the salivary 

 glands. The first of these is especially formed of three prominences, succeeding 

 each other in the median line, the lowest and most posterior of these being the 

 larger. They are covered by long papillae which are coated by a layer of long 

 columnar epithelial cells. Next to these, on the way to the oesophagus, comes the 

 odontophore. Its support is a horny, transversely striated .band in the space between 

 the sides of the lower mandible. Upon this lies, in the first place, the " radula ; " 

 consisting of about twelve transverse rows of horny and recurved teeth. Each 

 row has thirteen teeth — the five central are trapezoidal and point towards the oeso- 

 phagus ; the four outer on each side are two very long and pointed, alternating with 

 two short, flat and transverse. After the radula, the pharynx becomes papillose 

 again both on the upper and lower sides: the cushions developed on either jaw 

 bringing their papillae into contact. At the sides are two glandular organs which 

 have the apertures of their ducts at this part of the oesophagus, and which may 

 therefore be supposed to perform the functions of salivary glands. 



The oesophagus is very short, and almost immediately after passing a cartilage 

 (to be presently described) dilates into a large pyriform crop (fig. 5, g), the lining 

 membrane of which is tough and smooth, and which is provided with longitudinal 

 and transverse muscular fibres. Macdonald describes two little glandular bodies 

 connected with the crop by bundles of muscular fibres and by cellular tissue, but 

 which appear to have no ducts. • From the hinder end of the large crop a short tube, 

 with rugose and villose walls, leads into the gizzard (fig. 5, h). The muscles of this 

 radiate from a central point on each side, and it is lined with a furrowed chitinous 

 membrane, but contains no gritty particles. The shells of crabs, &c, which form the 

 animal's food, must be broken by mutual attrition. The pyloric aperture, which is 

 protected by a valve, takes its rise very near to, but below, the entrance of the 

 oesophagus. The alimentary canal is, therefore, said by Huxley to have a neural 



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