144 LOWER VERTEBRATES. 



dages. The body is elongate, compressed, and naked, or covered with very fine decid- 

 uous scales. The snout is long, flat, and pointed. They are small Goloriess fishes 

 living at considerable depths off the coasts of China, and Japan, approaching the shore 

 to spaven in their season. They are considered a delicacy, and to the English in China 

 they are known as whitebait, a name given in London to the translucent young of the 

 herring and other clupeoid fishes. 



The small family of smelt, or Aegentinidje, is separated by Dr. Gill from the 

 Salmonidse, with which they have many affinities, on account of the form of the 

 stomach and its appendages. In the Salmonidse proper the stomach is siphonal, 

 the oesophagus and pylorus being widely separated, and about the stomach are many 

 pyloric coeca. In the Argentinidae, the stomach is in the form of a blind sac, the open- 

 ing of the oesophagus and that of the pylorus being near together, and there are but 

 few, if any, pyloric coeca. Externally the two families are very similar. The Argentini- 

 dae are, however, small fishes, properly marine, while the Salmonida3 are rather fluvia- 

 tile in habit. About twenty-five species are known, all but one of them inhabiting the 



Fig. 93. — Osmerus mordax, smelt. 



waters of the North Temperate zone, and rarely passing southward of a latitude of 

 about forty degrees. Several of them are deep-sea fishes, while most of the others are 

 found near the shore, ascending the rivers in the spring, to deposit their spawn. Of 

 the anadromous species, many have a considerable economic value, as they furnish 

 excellent food. 



The genus Hetropinna, distinguished by the backward position of its dorsal, is 

 found in the waters of New Zealand, where its single species is known, not inappropri- 

 ately, by the name of smelt. The species of Microstoma, Argentina and JBathylagus, 

 are deep-sea fishes, not unfrequently taken in the Atlantic, and some of them even 

 venturing into comparatively shallow water in the northern regions. It is a somewhat 

 curious fact that many shore-fishes of the arctic become deep-sea fishes in the temperate 

 zone. None of these, however, inhabit the enormous depths in which many eels, stom- 

 iatoids, etc., occur. These deep-sea Argentinid^ are silvery in color and have no 

 phosphorescent spots. 



The genus Osmerus contains the smelt, characterizable by the presence of strong, 

 fang-like teeth on the tongue and on the vomer, and by the comparatively large size of 

 the scales, which are readily deciduous. One of the species, Osmerus eperlanus, is 

 common along the shores of northern Europe, A\here it is held in high esteem as a food- 

 fish. Another, ( Osmerus mordax), scarcely different from this, but with rather smaller 

 scales, is equally abundant on the American coast from Delaware Bay northward. 

 Both these species ascend fresh-water streams, and both in America and Europe, 

 stunted forms are found permanently land-locked in ponds and lakes. The flesh of 

 the smelt is rich and delicate, but it spoils quickly in warm weather. A third species 

 (0. thaleichthi/s), very similar, but smaller in size, and feebler in dentition, is found oil 



