CAT-FISHES. 561 



spine the second and third iaterneurals unite to form a single 

 plate, the "buckler;" the great spine is articulated to the 

 third interneural, and there is only the vestige of a spine on 

 the second interneural in form of a small oval bone, forked 

 below, whose function is to act as a bolt or fulcrum to the 

 great spine when the fish wishes to use it as an offensive 

 weapon. The great spine itself is joined by a ring to a 

 second spine, which belongs to the third interneural. This 

 articulation by ring exists in Lophius and a few other fishes 

 not of this family. 



The first interneural does not carry a ray, and it varies 

 much in the species whose helmet is continuous with the 

 buckler, as in many of the Bagri and Pimelodi. In these 

 cases the supraoccipital, extending backwards, conceals the 

 fiist interneural, passing over it to touch with its point the 

 buckler formed by the second and third interneurals. In 

 other instances, as in Synodontis and Auchenipterus, the supra- 

 occipital and second interneural, forking and expanding, in- 

 close and join themselves to the first interneural, but leave 

 a larger or smaller space in the middle of the nuchal armour 

 which they contribute to form. When the point of the supra- 

 occipital does not reach quite to the second interneural, the 

 first interneural remains free from connection, and occasion- 

 ally shows as a narrow plate interposed between the other 

 two ; in such a case the helmet is not continuous with the 

 buckler. 



The neural spines of the coalescent centra, which form the 

 apparently single first vertebra, concur also in sustaining the 

 nuchal plate-armour and the first great dorsal spine. They 

 carry the interneurals, are joined to them by suture, and one 

 of them is often inclined towards the occiput to assist in sus- 

 taining the head ; in fact, this part of the skeleton is con- 

 structed to give firm mutual support. 



The shoulder-girdle of the Siluroids is also formed to give 

 2o 



