288 LOWER VERTEBRATES. 



form and small, or reduced to spiiiiform appendages. The anterior dorsal fin is com- 

 posed sometimes of three spines, sometimes of one ; in the former case, the first spine 

 is the largest, and, when erect, is held in place by a peculiar articulation of the second, 

 which interlocks with it. In the others the fin is reduced to a single spine, which 

 may be far advanced forward, even upon the head. The ventral fins are entirely 

 wanting, but the pelvis is movable, and its extremity often manifested by a spiny 

 armature, although in others it is entirely concealed within the integuments. The teeth 

 are incisorial. The species arc numerous and represent several sub-families. 



The most common species of eastern America is one known as the trigger-fish along 

 the southern states, leather-jacket at Pensacola as well as at Key West, and in Ber- 

 muda it is even endowed with the name of the celebrated turbot. It is said by Mr. 

 S. Stearns to be "very common in the Gulf of Mexico, from Key West to the Missis- 

 sippi River." It "lives in deep waters near the coast, on the grounds where red- 

 snappers and groupers are caught. It is one of the most abundant species. In regions 

 where it is not eaten, it is regarded as a pest by fishermen, from its habit of stealing, 

 bait from their hooks. Its manner of taking the bait is rather peculiar," for, instead 

 of pulling the line downward or to one side, " it raises it upward so quietly that the fish- 

 erman does not perceive the motion, and then, by careful nibbling, cleans the hook 

 without injury to itself. Expert fishermen, however, can tell by the 'lifting of the 

 lead,' as it is called, what Is going on below, and know what they have to contend 

 against. The usual remedy is to seek other fishing grounds where the leather-jackets 

 are not so troublesome. When one of these crafty fish has been hooked, there is not 

 much probability that it can be landed ; for its sharp, powerful teeth are almost sure 

 to Cut some part of the gear, enabling it to escape." 5Ir. Stearns had " several times 

 known of their biting in two the large red-snapper hooks on which they were caught. 

 They remain throughout the year on the fishing gi-ounds, where the water varies from 

 ten to forty fathoms. On these same grounds it is probable that they spawn." 



Although rejected by many as food, it is by some, as in Bermuda, " considered a 

 valuable food fish." But it is not only as food that it is subservient to man. Mr. 

 Goode tells us that the skin is " used for scouring and polishing purposes at Key West 

 and the Bahama Islands. In the Bermudas, also, the skin of the turbot is used by 

 carpenters almost to the exclusion of sand-paper, the former being better adapted to 

 fine work in polishing wood." 



SuB-OrDEE II. — OSTRACODBRMI. 



A single family is the type of another order, which is intermediate between the 

 Scleroderms and some very specialized forms to follow. The characteristics of this 

 sub-order are the absence of a spinous dorsal, the development of the dermal covering 

 into a solid coat of mail composed of interlocking plates, and the presence of distinct 

 teeth in the jaws. 



The only family of the sub-order, Ostbaciontid^, is distinguished by its angular 

 polygonal form, the whole of the body except the caudal being encased in a series of 

 large and generally hexagonal plates, whose edges mutually join, leaving no laxity 

 whatever of the trunk. The teeth are compressed, curved, and sharp, in a single 

 row, and generally eight above and below. Not more than a couple of dozen species 

 are known, which appear all referable to two genera. The rigid box in which 

 the fishes are encased entail more use of the dorsal and anal fins than is customary 



