Linnaan Society. 267 



The ribs are thirty- six pairs, and consist of short, slightly curved, 

 slender styles, encompassing, with the spine, about one-sixth part of 

 the cavity of the abdomen. These ribs are attached to the lower part 

 of the side of the fibrous sheath of the central vertebral chord ; their 

 pointed free extremities are cemented to the intermuscular ligaments. 



The superior spines are throughout separated from the neurapo- 

 physes, and these are not anchylosed together at their upper extre- 

 mities. Hsemapophyseal spines are developed in the caudal region, 

 and both these and the neurapophyseal spines have articulated to 

 them dermo-osseous spines, of equal length, with their distal extre- 

 mities expanded, and supporting the transparent elastic horny rays 

 of the caudal fin. The rudimental filiform pectoral and ventral 

 fins were supported each by a single cartilaginous ray composed of 

 many joints. 



The muscles of the head, jaws, hyoid and branchial apparatus 

 were then described : the muscular system of the body consists of 

 subvertical layers of oblique fibres separated at brief intervals by 

 aponeurotic intersections. 



The following peculiarities of the Digestive system were then 

 pointed out ; — two long, slightly curved, slender, sharp-pointed 

 teeth project from the intermaxillary bones, which are moveable. 

 The upper maxillary bones support, each a single dental plate divi- 

 ded into three cutting lobes, by two oblique notches entering from 

 the outer side : the lower jaw is armed with a single dental plate si- 

 milarly modified, the produced cutting edges fitting into the notches 

 above : these maxillary teeth somewhat resemble the dental plate of 

 the extinct Ceratodus of Agassiz. The fleshy and sensitive parts of 

 the tongue are more developed than in fishes generally. The jaws 

 are adapted to minutely divide and comminute alimentary substances ; 

 the pharyngeal opening is contracted ; the entrance to the pharynx 

 guarded by a soft semicircular valvular process. Gullet short, straight, 

 narrow, but longitudinally plicated. Stomach simple, straight, with 

 thick walls, in capacity corresponding with the oesophagus ; termi- 

 nating by a valvular pylorus projecting with a scalloped margin into 

 the intestine. No pancreas or spleen. Liver well-developed, partly 

 divided into two lobes. A gall-bladder, and large ductus choledochus, 

 opening by a valvular termination close to the pylorus. Intestine 

 round, straight, at first of equal diameter with the stomach, but gra- 

 dually contracting to the vent, with thick parietes ; traversed inter- 

 nally by a spiral valve describing six gyrations ; the first of which is 

 the longest. 



The respiratory organs consist of branchiae, and a double elon- 



u2 



