64 SUPPLEMENT ON 



There still remains a kind of stylus, usually of two pieces (No. 

 49 and 50), the upper of which, partially flattened, is suspended 

 from the humerus (No. 48), adheres to its internal surface, and 

 to its posterior superior border, apparently representing the 

 coracoidian of the superior classes. There are some curious 

 modifications of these bones in the genera siganus, seserinus, 

 batrachus and cyprinus, while in anguilla, anarrhicas, and 

 silurus they are totally wanting. On the external border of 

 the ulna and radius (No. 51 and 52) are the flat bonelets, 

 compared to the carpus (No. 64). They bear all the rays of 

 the pectoral fin, except the first, which is planted on the 

 radius (No. 52). The bones of the carpus, and not those of 

 the arm or forearm, are prolonged in the genera lophius and 

 batrachus, where also they differ in number, as they do like- 

 wise in polypterus. The bones of the posterior extremities 

 of other classes are represented in fish by a single bone 

 (No. 80), usually triangular and complicated, variously sus- 

 pended, the ventral rays issuing from its posterior border. 

 All the rays of the extremities are divided longitudinally, 

 each into two parts. Excepting the external ray of the ven- 

 tral in acanthopterygians, they are almost always articulated, 

 and that exception is, as the name of the order imports, a 

 spinous bone. 



In this manner is formed the skeleton of osseous fishes, 

 including many genera improperly classed with the cartilagi- 

 nous division. Except as relates to vertebrae and rays of fins 

 they have all nearly the same number of bones in their com- 

 position, notwithstanding the great difference of form they 

 may present ; but the chondropterygians, really cartilaginous 

 in their structure, have a different skeleton, requiring some 

 notice. 



The pieces of the skeleton in rays and sharks have no 

 fibrous tissue characteristic of bone. Their interior remains 

 always cartilage, and their surface alone becomes hardened 



