35 6 SPINY-FINNED GROUP. 



as shown in the example of the type genus (Poly nemus plcbcj us), represented on the 

 left side of the illustration last referred to ; while a second characteristic is to be 

 found in the two rather short dorsal fins, situated at a considerable distance from one 

 another ; and a third in the well-marked mucous-bearing canals on the head. The 

 body is oblong and somewhat compressed, with smooth or slightly ciliated scales, 

 and a continuous lateral line. The muzzle projects somewhat beyond the mouth, 

 which is inferior in position, with a lateral cleft ; and the large eyes are lateral. 

 There are villiform teeth in the jaws and on the palate ; and the pelvic fins are 

 thoracic in position, with one spine and five rays. These fishes, which form three 

 genera, include a number of species haunting the shores of tropical seas, and some- 

 times entering brackish or fresh water. Their filaments, which sometimes exceed 

 twice the entire length of the head and body and can be moved independently of 

 the pectoral fins, serve as feelers ; and as these fish live in muddy water, and 

 generally have their large eyes obscured by a film, the use of such accessory organs 

 of touch is easily understood. 



The Solenoids, — Family Sci^nid.-e. 



Of more general interest than the last is the family of Sciamoids, among which 

 the umbrine of the Mediterranean and the widely distributed meagre are well known 

 examples. In this group the spinous dorsal is abbreviated at the expense of the 

 more or less elongated soft dorsal, which also exceeds the anal fin in length ; and, 

 although mucous canals are well developed on the head, there are no filaments 

 near the pectoral fin. The somewhat elongated and compressed body is coated 

 with ctenoid scales, and the uninterrupted lateral line sometimes continued on 

 to the tail-fin. The long mouth is at the extremity of the muzzle; the eye is 

 medium and lateral ; and in addition to bands of villiform teeth, the jaws may 

 carry tusks, although they are never provided with incisors or molars, and the 

 palate is devoid of teeth. The preopercular bone is smooth, and without any bony 

 connection with the orbit ; and the thoracic pelvic fins carry one spine and five 

 rays. Frequently the air-bladder is provided with a number of appendages. 

 These fishes have a rather curious geographical distribution, being unknown in the 

 Pacific and the Red Sea, but widely spread in the Atlantic and Indian Oceans, and 

 especially common round the shores of India, where many species enter estuaries 

 and rivers. Some species have, indeed, taken completely to fresh water, and never 

 by any chance descend to the sea. Nearly all are eaten as food, and the air- 

 bladders of many of the Indian forms are extensively used as a source of isinglass. 



The North American fish, rejoicing" in the name of " drum " 

 Drum. . . 



(Pogomas chromis), represents a genus characterised by the upper 



jaw of the convex muzzle overhanging the lower, the presence of numerous small 



barbels on the chin, and the absence of tusks. Ten stout spines form the first 



dorsal fin, and there are two spines in the anal, the hindmost of which is very 



strong. The scales are of moderate size ; and there are a number of large flattened 



molar-like teeth on the pharyngeal bones. In length the drum often exceeds 4 feet ; 



while it may scale upwards of 1 cwt. In what manner the extraordinary drumming 



sounds uttered by this fish, in common with other members of the family, are 



