202 SIXTH RKPORT 18.36. 



Our remarks on the amphibia will be still more brief than on 

 the reptiles. Some amjjhibia are evidently more capable of en- 

 during extremes of temperature than the reptilia, and they exist 

 in higlier latitudes ; frogs and salamanders reaching the 67th 

 parallel on the Mackenzie, where the mean temperature is not 

 above 7 or 8 degrees of Fahrenheit, and the winter colds some- 

 times descend to more than 90" below the freezing point, 

 Spallanzani relates that living frogs have been seen in the ther- 

 mal baths of Pisa, which have a temperature of 115° F. In the 

 fur countries the pools of melting snow swarm with very noisy 

 frogs long before the soil is thawed ; the office of reproduction 

 is performed and the pools di'ied up by the time that the ice 

 of the lakes is dissolved, and before the earth is sufficiently 

 warmed to permit the snakes to crawl forth from their subter- 

 ranean retreats. The principal genera rana, hufo, liyla, and 

 salamandra occur both in Europe and North America. The 

 genera siren and nienopoma belonging to the latter country, are 

 perfectly amphibious, the mature animals possessing both lungs 

 and gills, and respiring at pleasure either air or water. The 

 only analogous animal of the Old World is the proteus anguimcs 

 of the lakes of Lower Carniola, and the grotto of Adelsberg, 

 between Trieste and Vienna. I observed on the banks of the 

 Mackenzie a very singular looking tadpole which swarmed in a 

 pool of water in the spring. It was about the size of a man's 

 thumb, and its abdomen was greatly distended with fluid, but 

 its integuments were quite transparent, and so tender that they 

 burst on the slightest touch. Circumstances did not admit of 

 my describing it at the time, and the specimens put into spirits 

 were destroyed by accident. 



PISCES. 



The ichthyology of Noi-th America has not hitherto been at- 

 tended to as it merits, and the distribution of the species through 

 a very large portion of the northern hemisphere is still almost 

 unknown. Catesby, Pennant, and Schcepf are the chief author- 

 ities of older date, for the introduction of the American fish into 

 the systems, but tlic Linnean genera are so ill adapted for the 

 reception of many of the forms peculiar to the New World, 

 and the specific descriptions of the old writers are so brief and 

 indeterminate, that the labours of these naturalists are often 

 altogether unavailable to modern cultivators of science. Le 

 Svieur, the most accurate of recent American ichthyologists, has 

 described many species in the " Journal of the Academy of 

 Sciences of Philadelphia/' in the new scries of the " Trans- 



