78 ANNALS NEW YORK ACADEMY OF SCIENCES 



in the northern hemisphere. In fact, Osborn has already stated in "The 

 Age of Mammals" that the South American fishes show an ancient north- 

 ern affinity. The dipnoans and crossopterygians, which are now found 

 only in the southern hemisphere, also were northern in origin, as far as 

 we now know. 



The fact that South America has many species but few families of 

 fishes also vaguely indicates a northern origin, because both plants and 

 animals often rapidly break up into new species when placed in new 

 environments. If the Cichlidse were not northern in origin, how were 

 they able to get into Wyoming during the early Eocene, when they are 

 noAV not able to get north of Eio Grande and have never been able to 

 enter Patagonia? The mere fact that the characinids and cichlids are 

 still "going wild" in making species indicates that they entered South 

 America during or after the late Miocene, i. e., after South America be- 

 came permanently connected with North America. This view seems to 

 be all the more probable, because it appears to be easier for animals to 

 move from temperate regions to the tropics than vice versa. 



It must also be noted, before dismissing the subject of the point of 

 origin of the South American fresh-water fishes, that there is some vague 

 evidence in favor of the marine distribution of at least the Cichlidse and 

 Osteoglossidse. The genus Priscacara is closely related to the marine 

 Pomacentridse, according to Cope, and the formation in which they are 

 found appears to have been near the sea level. Hence, in view of the 

 fact that the actual paleotelic or ancestral forms which were distributed 

 are not definitely known, a marine distribution of many primitive forms 

 is not at all impossible. Such a view is made all the more probable by 

 actual experiment as already noted. 



The present distribution of the osteoglossidse can be explained most 

 easily by considering them as northern in origin, at least if the zoogeog- 

 raphers do not entirely ignore the paleontological evidence. It must be 

 admitted that there is no positive evidence to show that the Characinidse 

 are directly northern in origin, but the only positive evidence at present 

 known indicates that both the Cyprinidse and JSTematognathi, the nearest 

 relatives of the Characinidse, originated in the northern hemisphere, and 

 it is highly probable that the ancestral Ostariophysi were also northern 

 in origin — if we admit that the Ostariophysi are a homogeneous group. 

 In this connection, the Nematognathi appear to have first split off from 

 the ancestral Ostariophysi. Then the Cyprinidse split off, and some of 

 the later Ostariophysi were pushed, after the Miocene times, into South 

 America, and the Characinidse, now found in the southern hemisphere, 

 appear to be the lineal descendants of this ostariophysian stock and have 



