386 Dr. O. A. L. Morch on the Systematic Value of the 



higher terrestrial types. Even the form of the now-existing 

 continents seems to be subject to a certain definite plan. The 

 three main continents (1, Europe and Africa^ 2. North and South 

 America, 3. Asia and Australia) extending from north to south, 

 nearly forming a continuous range, show a remarkable resem- 

 blance in their configuration — towards the south a large tri- 

 angular mass of land without considerable gulfs (Africa, South 

 America, Australia) united by an isthmus (Suez, Panama, Ma- 

 lacca and Sunda islands) to a larger land with numerous gulfs 

 and peninsulas, forming a large median gulf (the Mediterranean 

 Sea, the Gulf of Mexico, Mindoro Sea) with numerous archi- 

 pelagos at the entrance (Canarian and Cape de Verde Islands, 

 West-India Islands, Phihppine and Molucca Pacific islands); 

 close to each of the southern parts is a satellite island with a 

 most remarkable aberrant fauna — Madagascar, New Zealand, and 

 Galapagos Islands. These three continents would geologically 

 be considered three different formations. Australia, probably the 

 youngest continent, representing the Liassic period of the Old 

 World, is characterized by the lowest Mammalia, viz. the abor- 

 tive Marsupial ia. America has only a few Marsupialia, fre- 

 quently without pouch (marsupium), but the greatest number 

 of the lowest Placentalia (Microsthena), the Edentata. Africa 

 has no Marsupialia, but a few Edentata, and abundance of the 

 higher Mammalia (Macrosthena). If an order is common to 

 the Old and New Worlds, there is always a marked difference 

 according to the continent, the species of the Old World belong- 

 ing to groups of a superior stamp. Thus the Quadrumana and 

 Scansores (Parrots, among birds, corresponding with Monkeys) 

 are divided into those of the Old and those of the New World 

 — the latter being chiefly long-tailed, a character considered 

 inferior. 



The Ampullaria of the New World are nearly all provided 

 with a siphon, which is wanting in those of the Old World. 

 The same is the case with the gennsPolT/mesodon in the Cyrenida, 

 and Leila among the Unionida. The difference between the 

 faunae of the three continents diminishes towards the north, 

 where the faunse are fused into one circumpolar fauna, like the 

 three continents themselves. The land-faunse are limited by 

 thermal differences or mountain-ranges. Species living in or 

 or close to water (e. g. Succinea) are very similar all over the 

 world. 



The three continents above mentioned divide the ocean into 

 three parts geographically, but not zoologically — the Atlantic, 

 the Pacific, and the Indian oceans. These are limited by the 

 following coast-lines : — 

 1. From Behring's Straits, Norway, Spain, Guinea, Cape. 



