396 Evolution and Distribution of Fishes 



fish, in structure of the fins, in number of vertebrae, in 

 presence of villous and often also of stronger or canine 

 teeth, and many other details, such a primitive gobioid 

 genus as Eleotris shows close agreement. Further if the 

 6 to 8 spines of the anterior dorsal fin-lobe in Eleotris were 

 condensed, moved forward, and split into jointed halves, 

 as Storms has suggested, the 12 laminae of the peculiar disc 

 in the fossil O pis thorny zon (Echeneis) glaronensis would 

 be explained. Continued subdivision of the rays, and con- 

 version into laminae would explain also the 17-25 laminae 

 in the disc of some modern species. A steady multiplica- 

 tion in number of the vertebrae also, from 24 or 25 to as 

 many as 27 - 30 is seen proceeding from the fossil to the 

 recent species. So from some primitive, probably early 

 Eocene genus allied to Eleotris, through the Oligocene 

 Opisthomyzon, and thence to recent species of Echeneis, 

 the steps seem to be progressive and fairly continuous. But 

 when we compare the less modified fossil type with existing 

 ones Storm's remark {258: 67) is appropriate for the for- 

 mer when he regards it as "a more normally shaped fish" 

 than any of the living representatives. 



The family Serranidae, already reviewed, was shown 

 to have early sent off from freshwater genera others that 

 became marine, and that speedily evolved a large series of 

 marine genera and species. This seems to have taken place 

 at least in early Eocene times, probably in mid or late 

 Cretaceous, and possibly in several separate centres of 

 evolution. For in distribution of the Serranidae over the 

 world, the same lines of voyaging were doubtless pursued, 

 that we have already outlined in previous pages, while the 

 regions reached were as diverse and often as remote. In 

 this process then groups arose in definite centres that, by 

 steady and continuous variations, became in time of family 

 value. 



So from the Serranidae new families must have branch- 

 ed off that are now wholly marine, and which constitute the 

 Pseudochromidae, with succeeding derivative families the 

 Sillaginidae and the Cepolidae. Again the Sparidae, 

 Mullidae, Gerridae, Sciaenidae, Latrididae, and Haplo- 

 dactylidae, are related families that show affinities and also 



