Cope.] * [April 17, 



slopes gently from the dorsal line ; hence the pectoral outline is very 

 steep. The head is a good deal injured in the typical specimen, but it is 

 somewhat longer than deep. 



The middle of the base of the pectoral fin is half-way between the ver- 

 tebral column and pectoral border inclusive. The dorsal fin begins along 

 the anterior border of the fourteenth vertebra. It is elevated in front, and, 

 having a short base, has a rapidly descending posterior outline. The anal 

 fin originates much behind the posterior border of the dorsal. It is also 

 short and weak. Formula, D. 10 ; C. -f 18 -f ; A. 8. Vertebrae, Abd. 

 24 ; C. 10 ; only one included between the external caudal rays. Neural 

 and haemal spines weak and rather short. Ribs long and robust. Abdom- 

 inal scuta rather large, and with a free posterior accumination. The sup- 

 plementary ribs, if they ever existed, are not preserved. Ventral fins lost 

 from the typical specimen. 



Measurements. M. 



Total length (axial) 126 



Length to basis of caudal fin 096 



Depth at free edge of operculum 044 



" " " " " dorsal 1st ray 055 



" " " " " anal " " 020 



Length of dorsal fin \ in front 016 



(. on base 014 



Length of anal finj iafront 007 



*- on base 010 



Length of a caudal lobe from base 035 



" " abdominal vertebrae 056 



" " caudal " 020 



The specimens are from the coast near Bahia. The type comes from 

 near Itacaranha, where it was found by Mr. Joseph Mawson. Other 

 specimens are from the same locality, while others are from Plataforma 

 and Agua Comprida. In none but the type do I find the dorsal scuta pre- 

 served. 



This genus has hitherto been only known from the Lower lacustrine 

 Eocene of North America. Its occurrence in this supposed marine forma- 

 tion indicates that, like its close ally Clupea, Diplomystus has considerable 

 range in time and space. The D. longicostatus falls into the section of the 

 genus represented by D. humilis Leidy. From this and the allied D. altus, 

 it differs in the more numerous abdominal and less numerous caudal ver- 

 tebrae, and the longer lobed more deeply furcate caudal fin. 



Ciiiromystus mawsoni, gen. et sp. nov. 



This new genus and species are indicated by a single large specimen 

 from the same horizon as the Diplomystus longicostatus. It is nearly com- 

 plete, with the important exception that the head and a few anterior dor- 

 sal vertebrae are wanting. The impression of the scapular arch, however, 

 gives the position of the skull, and the anterior ribs give a clue tp the 



