62 THE WASATCH AND BRIDGER FAr>"^. 



This order, so extensively developed in recent times, first appears in 

 geological history in a single genus in the Bridger Eocene. It has not yet 

 been found at a lower horizon than this. These earliest forms do not differ 

 widely from recent ones, so far as appears. 



RIIINEASTES Cope. 



Procced.Amer. Pbilos. Soc.,1872, p. 486 (published August 20, 1872). Annual Beport U. S. Geol. Surv. 



Terrs., 1872 (1873), p. 638. 



This genus differs from those at present inhabiting North America in 

 the presence of teeth on the vomer (B. cdlvus). The teeth are everywhere 

 coarsely villiform. The occipital bone exhibits a pit on the middle line 

 below, and a surface for attachment for the inferior branch of the post-tem- 

 poral on each side {JR. calviis, B. smithii). The modified anterior vertebrae 

 mass is deeply grooved below {B. smithii). The cranium is covered with a 

 rugose exostosis {B. peUatus, B. calvus, B. smithii), and has a strong closed 

 groove in the position of the usual fronto-parietal fontanelle. The verte- 

 brae (B. smithii) are short, and the sides of the centi'a only striate with the 

 circumference. There are no lateral pits, but a pair above and a pair 

 below, with a coossified apophysis at the base of one of them. 



The spines preserved belong chiefly to the pectoral fin. They are 

 strongly striate and weakly dentate, and have the usual hinge with superior 

 recurved flange above, and two embracing processes below at the base. 

 The dorsal spine is weaker in B calvus, but strong in B. peltatits. In the 

 former species it stands on the transversel}' expanded summit of the intert 

 neural bone, which presents a median process upwards and an articular face 

 on each side upwards and backwards. The median process is divided from 

 above, and the excavation receives a subglobular enlargement of the middle 

 of the base of the spine. This, with the two lateral facets of the basal 

 expansions of the spine, constitute the hinge on which the latter moves. 



This genus differs from those at present inhabiting the fresh waters of 

 North America, not only in the presence of vomerine teeth, but also in the 

 exostosis of the superior and lateral surfaces of the skull. The anterior 

 part of the cranium being absent from my specimens, I am not able to 

 determine whether Bhineastes should be referred to the Pimehdina or the 



