igoS] 



TRUE— ON THE CLASSIFICATION OF THE CETACEA. 387 



Miocene and Pliocene and is of comparatively large size, there is 

 an American form of squalodont which is either from the Oligocene 

 or Lower Miocene, and is of small size. 



This is the genus Agorophius. It is based on a skull from South 

 Carolina. It has serrate teeth like Squalbdon, but what is especially 

 remarkable, the parietals occupy a long area on the top of the skull, 

 wdiile in Sqiialodon and existing cetaceans the frontals and occipital 

 come together at the vertex so as to entirely, or almost entirely, 

 exclude the parietals. ° The very remarkable conformation of 

 Agorophius led Van Beneden and Gervais, and also Cope, to suspect 

 that it might possibly be the progenitor of the whalebone whales. I 

 do not think this is likely, but Agorophius appears to indicate that 

 Sqiialodon may have, and probably did, originate from forms very 

 unlike Zcuglodon. 



It might be supposed that the whole argument concerning the 

 derivation of the Cetacea from the zeuglodonts was negatived by 

 the occurrence of various characteristic forms of Cetacea in the 

 Eocene and even earlier formations, and hence contemporaneously 

 with, or earlier than, Zenglodon. In all such cases, however, so far 

 as I have traced them, the forms reported are really from the Mio- 

 cene. A notable case is that of the various important forms from 

 Chubut, Patagonia, described by Lydekker in 1893. These include 

 such genera as Scaldicetus and Paracetus, which certainly occur in 

 the Miocene of North America and Europe, and, indeed, I under- 

 stand the deposits at Chubut to be assigned at present without dis- 

 pute to the Miocene. 



The matter of the history and development of Sqiialodon is 

 especially important, as Professor Abel derives four families of 

 cetaceans from the squalodonts, namely, Physeteridse, Ziphiidse. 

 Eurinodelphidse and Acrodelphidse (or Iniidse), and one of them — 

 the Physeteridae — directly from Squalodon itself. The main argu- 

 ment in the latter case is that the teeth of some species of Scaldi- 

 cetus (or Physodon) — an intermediate genus — have a ridge on the 

 crown. This seems an unimportant character relatively, and does 

 not balance the difficulty of deriving the extremely concave skull of 

 Physctcr from the extremely flat skull of Sqiialodon. 



° See True, " Remarks on the Type of the Fossil Cetacean Agorophius 

 pygmceus (Miiller)," Smithsonian Publ., No. 1694, 1907, with i plate. 



