294 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.52. 



The supraoccipital process has been shifted slightly to one side of the 

 anterior vertebrae, and was apparently not in direct connection with 

 them. The relations are evidently very close ^vith the existing A. 

 catus, excepting as regards the smaller number of anal fin rays and 

 nonserrate character of the pungent pectoral spines. With respect 

 to the short-based anal fin, it may be said that although only a dozen 

 rays are now visible in the specimen, a few more may have been pre- 

 sent in advance of those now to be seen, but became lost or were cut 

 away by careless trimming of the specimen along the ventral margin. 

 In fact, one can almost certainly distinguish, although faintly, traces 

 of a few interspinous bones in advance of the foremost anal fin ray 

 now appearing in the specimen. At the most, however, we must 

 admit tliat this fin was shorter than in existing species of Ameiu7^s, 

 but othenvise the differences are of but minor character. 



The latter observation appears the more remarkable if we accept 

 the view as correct that the fossil before us is of Middle Eocene age. 

 How closely Rliineastes, from the Green River Eocene, agrees struc- 

 turally with modern species of Silurids, cannot be determined, as it is 

 known only by fragmentary remains. But in the nearly complete 

 skeleton which we are now considermg we find evidence that the 

 typical expression of the genus Ameiurus, as we know it to-day, was 

 already attained in the early Tertiary, and has persisted unchanged 

 over since. 



Formation and locality. — Supposedly from the Green River Eocene 

 of Wyoming. 



Family PERCIDAE. 



This family and the small one known as Aphredoderidae, now 

 nearly extinct, are included in Doctor Gill's superfamily Percoidea. 

 The types of most of Cope's species of AmpMphga, Asinepos, Erisma- 

 topterus, and Triclioplianes, belonging to the Apliredodcridae, are pre- 

 served in the collection of the United States National Museum. The 

 nearly complete example of TncJioplianes foliamm Cope, which has 

 recently been figured by T. D. A. Cockerell,^ is the property of the 

 American Museum of Natural History, and the types of Cope's species 

 of Mioplosus are divided between this institution and the National 

 Museum.^^ 



Fossil perches in the restricted sense of the term are represented in 

 the Tertiary rocks of this country by the genera Mioplosus, Plio- 

 plarclius, and Oligoplarchus. The first of these differs from Perca in 

 having fewer vertebrae and a spineless operculum. It is known by 

 several species in the Green River Eocene, of which the genotype, M. 

 lahracoides Cope, is the most common. Probably the so-called M. 



1 Amer. Naturalist, vol. 42, 1908, p. 571. 



2 For lists of specimens see the published catalogues of type and figured specimens belonging to these 

 museums, ah-eady referred to. The parts dealing with fishes were published in 1907 and 1908, respectively. 



