NATURAL SCIENCES OF PHILADELPHIA. ^ 



Trktosphys rv^sciienbercebi, Delphinaptcrus ruschmbcTgeri Cope, Proc. A. N. 



Sci., Pliila., 1868, 189. 



This is the smallest of the genus. It is known only from a caudal and 

 lumbar vertebra of one individual, from Charles Co., Maryland. 



ZARHACHIS Cope. 

 Proc. A. N. Sci. 1868, 189. 



Examination of additional material renders it necessary to correct the 

 characters of this genus as originally given. It was stated to diO'er from 

 Priscodelphinus in that, while some caudals had spinous diapophyses, others 

 possessed them flat, hut imperforate. A vertebra supposed to indicate the 

 latter characters I am now compelled to refer to another species and probably 

 a genus. Other vertebrfe assigned to Z. flagel later, must be referred 

 elsewhere. A lumbar vertebra represents another species of probably the 

 same genus, while a third has evidently pertained to still a third species. The 

 genus will be characterized by the extraordinary length and slenderness of the 

 lumbar vertebrae, and similar, though slightly abbreviated form of the caudals. 

 The latter have spinous diajjophyses, and in one species the former also. 

 While the width of the articular faces of the centra of these vertebraj in the 

 typical Priscodelphinus is but few lines less than the length, in the species of 

 this genus the diameter of the same is only from four-sevenths to one half the 

 length. The nearest approach is made by Priscodelphinus s t e n u s, m., 

 where this diameter is 6-7ths of the length. 



The three species of Zarhachis may be distinguished as follows : 



I. Median or anterior caudal with a strong longitudinal keel above the diapo- 

 physis — which is therefore probably present on the distal lurnbars. 



Epiphysis thicker, larger Z. flagellator. 



II. No longitudinal keel on lumbars. Diapophyses broad, flat; epiphyses 

 thin; large Z. tysonii. 



Diapophyses narrow, subspinous; epiphyses thin; small Z. velox. 



Zarachis flagellator Cope, Proceed. Acad. Nat. Sci., Phil., 1808, 189, pars. 



The caudal vertebra, described as above, is the only indication which we 

 have as yet of this large adolphin. 



Miocene, Charles Co., Md. 



Zarhachis tysonii Cope, sp. nov. 



This species is established on one posterior lumbar vertebra only, but its 

 form is so characteristic as to render its identification a comparatively simple 

 matter. The attenuated form characteristic of the genus is accompanied by 

 broad diapophyses, showing that, as in Priscodelphinus, the species differ in 

 the number of the posterior vertebrae which exhibit the contraction of the 

 diapophyses. 



The sjjeciraen preserved belonged to an adult animal. It was apparently 

 one of the most posterior lumbars, as there are two feeble longitudinal ridges 

 beneath, whose interval is again obtusely ridged and perforate by several 

 foramina. The inferior outline is stronglj^ concave in longitudinal section, 

 and all the planes are concave in transverse section. The articular faces are 

 a little wider than deep. The neurapophyses occupy a base of -75 the length 

 of the centrum. The diapophyses are about equidistant between them and the 

 nearest inferior ridge. 



Lines. 



Total length centrum 48 



Transverse diameter articular face 29 



Vertical " " " 27 



Width neural canal (internal) 5 



" between inferior ridges ,■ 8 



This specimen was found at the miocene beds at the mouth of the Patuxent 

 River, Maryland. It is water worn, and has been probably washed from the 

 clitfs, and been covered by the tide. 



1869.] 



