FISHES. Ill 



either naked or more or less covered with bony plates. The anterior vertebrae are 

 coalescent, as in the cyprinoid fishes, and the air-bladder communicates with the 

 organ of hearing by means of auditory ossicles. The bones of the skull are grown 

 together in a greater degree than in ordinary fishes, and the brain is somewhat differ- 

 ent, the cerebrum being (in some species, at least) rather better developed, and show- 

 ing a rudiment of the Sylvian fissure. 



The chief osteological character of the Nematognathi are thus summed up by 

 Professor Cope : " Parietals and supraoccipital confluent, four anterior vertebrae 

 co-ossified, and with ossicula auditus. No mesopterygium. Basis cranii and pterotic 

 bone simple ; no coronoid bone. Third superior pharyngeal bone wanting, or small 

 and resting on the fourth ; second directed backwards. One or two pairs basal bran- 

 chihyals: two pairs branchihyals. Suboperculum wanting. Premaxillary forming 

 mouth border above. Interclavicles present." 



Those features of the order which appear to the ordinary observer most striking 

 are the presence of the maxillary barbels above noticed ; the presence, in most cases, 

 of additional pairs of barbels about the mouth, near the tip of the upper or the lower 

 jaw, or both ; the absence of scales, and the presence, in many species, especially those 

 found in tropical waters, of bony plates. These sometimes form a more or less per- 

 fect coat of mail on the sides of the body ; at other times, they form a shield on the 

 top and back of the head. Anotlier feature is the development, in most cases, of the 

 first ray in the dorsal and pectoral fins as a strong, stiff, sharp, serrated spine, Avhich 

 forms an effective weapon of defence. The spines of the pectoral fins are strongest, 

 and they are usually 'set,' that is, firmly erected, whenever the fish is caught or 

 attacked. These spines are a source of much annoyance to fishermen, and there are 

 few persons who have ever been boys and fished in the creeks or millponds of the 

 eastern states, that have not bad some painful experience with the ' horns ' of a 

 cat-fish. Thoreau speaks of the cat-fish as "a blood-thirsty and bullying race of 

 rangers, inhabiting the river bottoms, with ever a lance in rest, and ready to do 

 battle with their nearest neiglibor. I have observed them in summei-, when every 

 other one had a scar upon his back where the skin was gone, the mark of some fierce 

 encounter." 



The articulation of the pectoral spine is somewhat peculiar. When erected, it 

 cannot be depressed directly, without breaking it, but by rotating it toward the 

 animal it can be laid down without difficulty. This is equally easily done, whether 

 the animal be dead or alive. 



The wounds made by the spines of the cat-fish are often painful, and sometimes 

 heal with difficulty. This seems to be due, not to any specific poison, but to the 

 jagged character of the cut, and to the slimy skin which is rubbed off from the spine. 

 In one genus, however (JVbticrics), there is certainly a poison gland connected with the 

 pectoral spine. 



Another characteristic of most of the Nematognathi is the presence of an adipose 

 dorsal fin, as in the Salmonidae, Characinidae, etc. In some cases this adipose fin has 

 distinct rays, and in others it is supported by a stiff spine. 



The teeth in all the Nematognathi are small and sub-equal, villiform or granular, 

 or in some cases, entirely wanting. The air-bladder is usually large, and is connected 

 by a slender duct with the oesophagus, as in other « soft-rayed ' fishes. The ventral fins 

 are present, usually eight to ten-rayed, without spine, and abdominal in position. 

 The anal fin is without spine and usually long. 



