The Spine-finned Teleostei 387 



state In the Pomacentrldae, where the teeth are still pointed, 

 conical, and even delicate. It becomes greatly more pro- 

 nounced in the Labridae, where the upper and lower pharyn- 

 geals become studded with rounded teeth like pavement- 

 knobs (Fig. 67). The jaws also become correspondingly 

 shortened and parrot-like. Finally the Scaridae have short 

 compressed mouths and jaws lined with dense crushing teeth 

 (Fig. 68) while the lower pharyngeals In them reach the 

 climax of specialization. One need merely note in passing 

 the exact analogy established here with the evolving groups 

 of the Pycnodonts, which curiously enough gradually passed 

 seaward, as did the Labridae and Scaridae, when under- 

 going the above progressive changes up to the point of 

 extinction. 



When the geographical distribution of the genera and 

 species of Pomacentrldae, Labridae, and Scaridae Is studied, 

 the conditions and relations seem utterly confusing and 

 hopeless for explanation. But if we accept that the prim- 

 itive ancestors were derived from Centrarchids, or even 

 more likely from some type like Etheostoma of the Percl- 

 dae, that existed in lakes of western or south-western N. 

 America, during late Cretaceous or early Eocene time, the 

 first necessary explanation Is obtained. If next it be con- 

 ceded that during late Cretaceous or early Eocene time such 

 land bridges existed as have been outlined by Koken and 

 Arldt (256 : charts 19, 20) also that prepared by the writer 

 as Figure 35, p. 240 — and which are abundantly verified in 

 their approximate outlines at least by the distribution of 

 many organic groups — a second and equally helpful aid 

 toward explanation Is got. 



We can now gather up. In as condensed manner as 

 possible, the geographical distribution of each of the three 

 above large groups. The Pomacentrldae is made up of 

 about 160 species Included under 8 or 9 genera, of which 

 the three most important are Glyphidodon with about 55 

 species, Pomacentrus with 45, and Heliastes with 16, and 

 these we may alone observe further. Glyphidodon has 2 

 species In tropical Atlantic and Carribean seas, 2 species on 

 the coasts of Cuba and Barbadoes, i on the tropical Atlantic 

 and Pacific coasts of Central America (that would Indicate 



