35 



limits assigned by Dana to the " Torrid Zone or Coral-reef Seas," 

 including all between the isocrymes of 68 F. , the reasons urged 

 by Dana being quite satisfactory. " In adopting these lines in 

 preference to those of other degrees of temperature we have been 

 guided by the great fact that the isocryme of 68 is the boundary 

 line of the Coral-reef Seas. ' ' * The existence of these fixed ani 

 mals, and the reefs which they elaborate, are among the best of 

 living thermometers, and the numerous forms that are associated 

 with, or dependent on, them for flourishing life concur to make them 

 the most reliable indicators and coincidents of temperature. The 

 characteristic types are very numerous, and among the families 

 nearly or quite confined to it, but common to all its subdivisions, 

 are, of fishes, the Muraenidae, the Ophichthyidae, the Albulidae, the 

 Synodontidae, the Scombresocidae, the Sphyrsenidae, the Priacan- 

 thidae, the Serranidae, the Chilodipteridae, the Mullidae, the Pseudo- 

 chromidae the Carangidae, the Chaetodontidae, the Acanthuridae, 

 the Polynemidae, the Gerridae, the Pomacentridae, the Labridae, (ex 

 cept Labrinae,) the Scaridae, the typical Scorpaenidae (Vert. 10 + 

 14,) the Eleotrine Gobiidae, the Antennariidae, the Triacanthidae, 

 the Balistidae, the Ostraciontidae, and the Diodontidae. The few 

 representatives of these families or sections which occur in temper 

 ate seas are chiefly summer wanderers, although a few have estab 

 lished themselves beyond their legitimate realm. With these are 

 associated numerous invertebrate types, many of which the most of 

 you will be able to recall. It includes a portion of the Floridian 

 coast. 



IV. THE NOTALIAN REALM. 



Notalia, or the south temperate realm, may provisionally be said 

 to extend from the southern isocryme of 68 to that of 44. Like 

 its northern analogue, it is distinguished by the commingling of 

 modified derivatives from the cold and equatorial realms rather than 

 by peculiar family types. Among the most noteworthy and char- 



*DANA, op. cit., p. 155. 



