62 HIGH SCHOOL ZOOLOGY. 



allied to the Esocidae may be mentioned the Umbridae, one 

 species of which, the little mud-minnow {Umbra limi), is to be 

 found widely distributed in muddy ditches. The mud-minnow 

 is in some respects allied to the Blind-Fishes of the Southern 

 fetates (Amblyopsidse ), the best known of which and the largest 

 is A. spekeus from the subterranean waters of the Mammoth 

 Cave, Kentucky. In accordance with the subten^anean life 

 the Blind-fish is colourless, the eyes are extremely rudimentary, 

 but the sensitiveness of the skin is increased by tactile organs 

 like those described in § 9, which are elevated on rows of papillae 

 above the general level of the skin. In all this family the 

 intestine turns forward and opens underneath the throat. 



14. The last Physostomous family to which reference need be 

 made is that of the Anguillidae, chiefly marine forms, but 

 represented in our inland waters by the common Eel (Anguilla 

 rostrata). The absence of ventral fins, the confluence of the 

 unpaired fins round the tail, the absence of hard rays, and the 

 rudimentary scales embedded in the soft skin, are some of the 

 chief superficial peculiarities of the group. Allied families are 

 those to which the Bengal Ampliipnous belongs, which has an 

 air-sac communicating with the gill-cavity, and the Brazilian 

 Gymnotus or Electric Eel, in which as in Malapterurus the 

 muscles of the tail are converted into an electric organ. 



15. PhysOClysti.— In this division of Teleosts the ventral 

 fins are usually in the course of their development shifted for- 

 ward till they attain a position either beside or in front of the 

 pectoral fins : they are then said to be thoracic or jugular. The 

 unpaired fins have generally hard rays. This is especially the 

 case in the Acanthopteri, the largest of the orders of Teleosts, 

 to which a vast number of marine forms belong, but which are 

 also represented in fresh-water" by the bass and perch tribes. 

 Although the air-bladder never communicates with the ali- 

 mentary canal in the adult, yet it is developed from it in the 



