1896.] ,141 [^Cope. 



3IETOPOCETUS DURiNASus, geii. et sp. nov. 



Char. gen. — Lateral occipital crests continuous with anterior temporal 

 crests which diverge forwards. Frontal bone elongate, not covered 

 posteriorly by the maxillary, coossified with the nasals. Xasals short, 

 coossified with each other, not projecting anterior to frontals. 



Accompanying the cranial fragment on which this genus is founded 

 is a piece of a premaxillarj" bone of appropriate size, which presents the 

 character of that of a whalebone Avhale. The true position of this 

 genus is probably between Cetotherium and Agorophius. It is probably 

 a mysticete which approximates the ancestral zeuglodont type which is 

 represented in our present: knowledge by the genus Agorophius. It is 

 connected with Cetotherium by the new genus Cephalotropis, Avhich is 

 described below. The three genera form a group, which may be 

 properly referred to the BalsenuUe, which is characterized by the elonga- 

 tion of the frontal and parietal bones on the superior walls of the skull. 

 They differ as follows : 



A temporal ridge ; maxillaries little produced posteriori}' ; nasals not 

 produced beyond frontal, coossified with the frontal and with each 



other Metopocetus Cope. 



A temporal ridge ; maxillaries much i)roduced posteriorly ; nasals free 



from frontals and from each other, produced well anteriorlj' 



Cephalotropis Cope 

 No temporal ridge ; maxillaries much produced posteriorly ; nasals free 



from frontals and from each other, well produced forwards 



Cetotherium Brandt. 



The specimen on which the genus Metopocetus is founded is quite 

 mature so that the sutures are coossified. The frontomaxillary and 

 froutopremaxillary sutures are however distinct, as they appear to me, 

 and they are remarkable for their position. They extend but little 

 posterior to the external nareal openings. The latter are, in relation to 

 the supraoccipital crest, anterior, but in relation to the position of the 

 nasals, posterior. The nasals are short for a Bal^enid, although they 

 enter wedge-like into the frontals for a considerable distance. 



The position of the genera Metopocetus and Cephalotropis may be 

 similar to that of the genera Ulias and Tretulias, which are known from 

 mandibular rami only. One or both of the former may be identical with 

 one or both of the latter ; but of this there is as yet no evidence. 



Char, specif. — The specimen which represents the Metopocetus duri- 

 nasus is a cranium posterior to the nares, lacking the left exoccipital and 

 squamosal regions, and the right zygomatic process. Both occipital 

 condyles are preserved, and the basicranial region as far as the anterior 

 nares. 



The supraoccipital extends well forwards and its lateral crests present 

 a moderate concavity outwards and forwards. Its apex is represented 

 by a semicircular mass, posterior to which it is deeply concave, and the 

 concavity is divided by a longitudinal median crest. The temporal 



