PEECOMOKPHI. 79 



As at the Green River locality, so at Twin Creek, this Herring is the 

 most abundant species One-third the entire number of specimens are 

 referable to it. 



DiPLOMYSTUS ALTus Leidy. 



Cope, Bulletin U. S. Geol. Siirv. Terrs., 1877, p. 811. Clupea alta Leidy. Final Eeport U. S. GeoL Snrv. 



Terrs., i, p. 196 



Plate XVII, fig. 2. 



This small Herring is abundant in the Green River shales, both at 

 Green River and at Twin Creek. It is distinguished from the D. humilis by 

 the greater relative depth of the body, resembHng in this respect the D. 

 pectorosus. The difference which it presents in this respect is rather too 

 great to permit its union with D. humilis. Nevertheless intermediate speci- 

 mens occur, but their characters are sometimes found to be due to distortion. 



Formulge:— Radii: D. I. 11; A. 1. 13-15. Vertebra: D. 22; C. 12. 

 Depth to length (without caudal tin) as 4 to 8. Size that of the D. humilis. 



PERCOMORPHl. 



Cope, Proceedings American Association for the Advancement of Science, 1671, p. 341. 



Physoclystous Actinopteri, with the shoulder-girdle attached to the 

 skull, and thoracic or jugular ventral fins. Maxillary and dentary bones 

 distinct; cranium symmetrical; epiotics normal; no interclavicles ; post- 

 temporal not coossified with cranium. Basal pectoral radii not enlarged ; 

 femora suspended (generally) from the scapular arch. Basibranchials thi-ee; 

 superior pharyngeals with the third usually the largest; sub and interoper- 

 culum present, plate-like. 



Three families are represented in the Eocene Tertiary beds, two of 

 which certainly belong to this order, and the third very doubtfully. The 

 former are the Percidce and IPomacentridcB, representing the suborders 

 Distegi and Pharyngognathi, respectively. The third group, represented by 

 the genera Amphiplaga, Trichophanes, and Erismatopterus, is related to the 

 AphododiridcB ;* and as I know of no characters as yet by which to distin- 

 guish it, shall for the present consider it under that head. This family lies 

 on the extreme verge of the order towards the Haplomi, to which the genus 

 Erismatopterus almost affords a transition. 



* This name is variously spelled, and I am not yet suie as to the orthography to be adopted. 



•^^ 



