NO. 8 INTERRELATIONSHIPS OF THE CETACEA WINGE Jl 



Pafriocefus one would expect that the two genera would resemble 

 each other in this particular also ; but according to Abel's representa- 

 tion Pafriocefus is here like the whalebone whales. According to 

 the photographic illustrations which accompany Abel's paper it is 

 scarcely possible to see whether his exposition of the conditions is 

 right or not ; the skull is too weathered and obscure. There is, how- 

 ever, a detail in his description of the boundary between the maxillary 

 and frontal, which probably must be wrong or at least must awaken 

 doubt. He says of the maxillar}- that it, at its postero-internal ex- 

 tremity, does not extend nearly so far backward as the nasal process 

 of the intermaxillary, which, on the contrary, like that of other whales, 

 extends up, far backward, alongside the outer margin of the nasal 

 and beyond. But there is elsewhere no cetacean, either among the 

 Archccocefi, Mysfacoccfi, or Odonfoccfi, in which the maxillary does 

 not reach postero-internally as far back as the intermaxillary or even 

 further, pushing itself up over the frontal. This is an inheritance 

 from ancestors among the carnivores or from yet more distant fore- 

 runners. Abel says, it is true (/. c, p. 162) that Pafriocefus in this 

 regard resembles Rhachionccfcs, one of the recent whalebone whales ; 

 but this is an error. In one of the figures of the skull of Rhachi- 

 ow^cfc?/ published by Andrews (1914, /. c, pi. 25) it can be clearly 

 seen that a long process from the maxillary extends along the outer 

 side of the intermaxillary to its hindmost end ; and it is so described 

 by Andrews (p. 261). In the second of Andrews' figures the process 

 is not visible ; it is obviously broken ofif, as it is in the figures pub- 

 lished by Van Beneden (Bull. Acad. Roy. Sci. etc., de Belgique, 

 ser. 2, vol. 43, No. 2, February, 1877, pi.) and True (1904, /. c, 

 pi. 47, fig. i), both of which represent the same skull (it is True's 

 figure to which Abel refers). A similar injury no doubt must have 

 been suffered by the skull of Pafriocefus; and if this process can be 

 broken away without leaving visible traces behind it the same might 

 be possible in the case of a thin plate-like process that originally 

 covered the supraorbital process of the frontal. How readily some- 

 thing of the kind can take place is shown by the type of Agorophius 

 (figured by Leidy, under the name Squalodon pygmccus, Journ. Acad. 

 Nat. Sci. Philadelphia, ser. 2, vol. 7, 1869, pi. 29, and by True, 

 Smithsonian Inst. Special Publ., No. 1694. 1907, pi.) : on the right 

 side of the skull large parts of the plate-like outgrowths from the 

 maxillary over the supraorbital process of the frontal are broken away 

 without having left behind any conspicuous traces on the frontal. 



