SKELETON. 



XV 



concave b'ones is covered in by connecting ligaments, and filled with a 

 gelatinous substance, the remains of tho • notocord : consequently, elastic 

 balls of semi-fluid consistence exist between each vertebra, enabling them 

 to move very freely one upon another. 



Tho abdominal vertebras, or those belonging to the trunk, have two 

 superior or dorsal processes, which pass upwards and coalesce, forming an 

 arch, the neur-al arch, which contains the spinal cord. At the summit of 

 this arch is a spinous elongation, the neural spine. Two transverse processes 

 generally pass outwards from the body of each vertebra, and to them ribs' 

 are commonly articulated. 



' The caudal vertebras, or those of the tail, are furnished with neural arches, 

 and spines as in the abdominal region, but well-developed transverse pro- 

 cesses arc deficient, while along the inferior surface of the bodies of each 

 vertebra is an arch, similar to the neural arch on its upper edge, and this 



rjUAiWJ^ 



Fig. 3. Skull of the Cod, Qadus morkua. 

 s,o, Supra occipital ; /, Frontal ; n, nasal ; p, s, Tara sphenoid; p, m, pre-maxillary ; m, max- 

 illary; d, Dcntary; I, pre-orbital ; q, Quadrate; 7i, m, Hyo-mandibular; p,o, Pre-opercle; o, Opercle; 

 s,o, Sub-opcrcle; i,o, Inter-opercle; c, h, Cerato-hyal ; b, Branchiostegous rays. 



lower or haomal arch serves to convey blood-vessels, while from it springs 

 inferiorly a haemal spine. ' ' 



Between the neural spines and the haemal spines certain dagger-shaped 

 bones arc inserted along the median lines of the body, and which are 

 externally for the purpose of attaching the bases of the dorsal and anal fins. 

 The hindmost caudal vertebra, usually of small size, articulates posteriorly 

 with a fan-shaped bone, the hypural, which along with tho last neural and 

 hsamal processes support the caudal fin. Among the plagiostomes the 



