ZOOLOGY. 415 



Old World. Already some of the dissections and observa- 

 tions of its inhabitants have made important contributions 

 to science. The first complete dissection and structural de- 

 scription of the manatee (Manatus americanus) was made 

 from its specimens, and some valuable contributions to com- 

 parative anatomy and physiology have resulted from their 

 observation. 



Geographical Distribution of Animals. 



It is now known that numerous marine animals occur in 

 inland lakes and rivers. Several species of Plennius are 

 found in the fresh waters of Southern Europe, says Profess- 

 or Duncan, in a resume, of this subject. Gobius is a fresh- 

 water East Indian fish. Pakemon jamaicensis is a fresh-wa- 

 ter shrimp; another small shrimp, allied to certain marine 

 ones, occurs in the fresh waters of Italy, and another shrimp 

 lives in the Mississippi as far north as Cairo, 111. The blind 

 fish of the Mammoth Cave are probably descendants of 

 marine forms. The Monolistra of the Adelsberg caves is a 

 fresh-water representative of a Sphmroma which lives in the 

 Pontine Marshes. Again, several families which are marine 

 in the Mediterranean Sea, such as the scomberoids, skates, 

 and rays, are represented in the tropics by fresh-water forms. 

 Monocbms polyacanthus (Haeckel) inhabits the Rio Negro. 

 Carcharias gangeticus is found sixty leagues from the sea ; 

 Pristis pevroteti lives in the Senegal. Iiaia fluviatilis has 

 been taken near Rainpur, nearly 1000 miles above tide reach ; 

 and Schomburgk found a Trygon in the river Magdalena. 

 The land-crab of the West Indies is represented in fresh wa- 

 ter by a Telphusa, though all the other crabs (JBrachyura) 

 are marine. Certain mollusks, usually marine in their hab- 

 its, are known to live in streams or lakes. Among Polyzoa, 

 Hlslopia lives in fresh water, and the hydroid Cordylophora 

 is a fresh-water form. In the lakes of Sweden, Switzerland, 

 and North America are marine species which have survived 

 the gradual change from salt to fresh water, while it may be 

 regarded as a general rule that all terrestrial and fresh- wa- 

 ter life has originated from marine forms, though this rule 

 may have had its exceptions. 



Among recent papers on the mammals in the Proceedings 

 of the Zoological Society is an essay on the Molossus bats, 



