The Spine-finned Teleostei 395 



that most of the other species had already completely ef- 

 fected the change. We have no hesitation in saying that 

 the latter supposition is devoid of real support. 



Other species spreading eastward, have become dis- 

 tributed in exactly similar manner to the combined Cichlidae, 

 Labridae, and Scaridae, over the rivers, more rarely along 

 the coastal regions, of the East Indies, and even northward 

 in a few cases to rivers or coasts of China-Japan, as well 

 as southward, in one species, to the rivers and coasts of 

 New Zealand. The air-bladder in all of these is large. 



The 13 species of Sicydhnn are all freshwater, and 

 are decidedly more evolved than is Eleotris. One only is 

 W. Indian, 2 are found in Bourbon and Isle de France, the 

 remainder are E. Indian. 



In contrast to Eleotris and Sicydium the large genus 

 Gobiiis, that includes about 160 species, has 125 marine 

 species, 8 that show marked adaptability to marine or 

 freshwater life, and only 25 that are freshwater. Of the 

 last however 6 are American. The distribution of the 

 freshwater and of the anadromous species makes it toler- 

 ably certain that, apart from an early migration of some 

 into the sea in Central America, many species may have 

 expanded eastward in freshwaters, during Oligocene time, 

 along the remnant of the S. Atlantis continental bridge, and 

 working eastward may have given off here and there at 

 intervals, shoreward migrants, that became in time the 

 organic foci for evolution of new marine species. But 

 highly detailed specific studies could alone satisfactorily 

 determine such a possibility. Like marine forms in general, 

 and in contrast to Eleotris, the air-bladder is usually ab- 

 sorbed. 



The small and remarkably modified group of the shark- 

 suckers or Echeneididae have been very variously viewed 

 by ichthyologists. As will be indicated by comparative 

 statistics later the group exhibits characters that would 

 place It In or near the family Goblidae, as suggested by 

 Miiller and later by Jordan, instead of in the Scombrldae 

 as advocated by Guenther and later by Storms, who protests 

 that "none of the characters of Echeneis glaronensis point 

 toward the Goblidae." On the contrary in shape of the 



