NATURAL SCIENCES OF PHILADELPHIA. 189 



ZARHACHIS Cope. 



This genus is established on vertebrje which bear a general resemblance to 

 those of Priscodelphinus, but differ in the essential point of having flat and 

 broad diapophyses of the caudals. It is therefore intermediate between that 

 genus and Delphinapterus. The posterior of the caudals in our museum ex- 

 hibits a narrowing of the diapophyses, as certain of the4umbars do in Prisco- 

 delphinus. 



Zarhachis flagellator Cope. 



This species is represented by only two lumbar and two caudal vertebrae, 

 which belonged to at least three different individuals, none of them adult. 

 Neither is any one entirely perfect, but they indicate a very distinct species, 

 by clear characteristics. All these vertebrteare of greater length as compared 

 to the diameter than in any other cetacean known by me except the great 

 Basilosaurus. The lumbars, when compared with those of T. lacertosus, 

 differ in tlieir broadly obtuse median line, which offers distinct trace of the 

 two keels. An anterior caudal either exhibits unusually broad diapophyses, 

 which are directed downwards, or else is a lumbar with two keels, ai^ 

 a median groove below, which is not seen in anj^ other species. The caudals 

 exceed in length those of any other species. One of these, from a large indi- 

 vidual, resembles that of P. a t r o p i u s in the narrow basis of the diapophysis, 

 which is ])robably narrow, and not perforate. The length of the vertebrae is 

 nearly double the vertical depth of the articular faces. The diapophysis is 

 nearly median ; the basis of each neurapophysis is one-half the length of the 

 centrum, and median. 



In. Lin. 



Length lumbar (epiphyses hypothetical) 3 6 5 



Depth 2 2 



Width 2 3 



" neural canal r 2 8 



Length caudal (one epiphysis supplied) 3 10-5 



Depth " 2 4 



Distance between inferior keels 10-5 



Width basis diapophysis 10-5 



DELPHINAPTERUS Less. 



Delphinapterus ruschenbergeri Cope. 



This species is represented by two vertebras, a lumbar and a caudal, which 

 indicate an animal of about the same or a little larger size than the Prisco- 

 delphinus s te nu s. They are also of a slender form, more so than in any 

 species of the last genus. What distinguishes it generically, is that instead of 

 the slender diapophyses of the caudal it has the broad ones of the true Dol- 

 phins, though broader even than is usual in these, and it is perforated a little 

 on one side of the middle by the foramen seen among Whales and Dolphins 

 generally. 



Articular faces transverse oval ; centrum slightly constricted with an 

 obtuse keel along the median line. The two inferior keels of the caudal vanish 

 on part of the middle of the centrum. 



In. Lin. 



Length centrum 1 9 



Height " , 10-3 



Width " 12 5 



" neural canal 5-2 



" basis diapophysis lumbar. 10-5 



« " " caudal 10- 



A dorsal vertebra which relates in age and size with the preceding, is 

 more than usually constricted lateromedially, the inferior line concave, and 

 slightly keeled; length 1G|- 1., width 12-5 1. 



1868.] 



