92 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 72 



grown together in a very long symphysis menti. They are staff- 

 shaped, each with a cup-hke pit left by a large tooth at the very front, 

 a somewhat indistinct alveolus further back, and also with more or 

 less indistinct traces of other teeth in a degenerate dental groove. 

 Abel (Odontocetes du Bolderien, 1905, p. 92) compares Anoplonassa 

 with iPalccosiphms; but True is no doubt right in finding a greater 

 likeness to " Miosiphius" {=Xiphirostrum). However, Anoplo- 

 nassa is still too slightly known to be exactly placed. 



" Palcrodphins" is established by Abel (Odontocetes du Bolderien, 

 1905, pp. 90-94, with figure) on the basis of a piece of the anterior 

 end of a lower jaw from the Tertiary at Antwerp. The specimen had 

 previously been referred by others to Champsodelphis and by Abel 

 himself doubtfully to Acrodclphis { = Champ sod el phis) . The jaw 

 has a long symphysis menti and a long series of alveoli left by good- 

 sized teeth. Abel says of it with great positiveness that it belonged to 

 a member of the family " Ziphiidce " (a group that about corresponds 

 to the Xiphnni of the present paper ; it was, he thinks, one of the 

 first links in the series that leads from the oldest, many-toothed 

 Ziphiids to the living two-toothed forms. His reason for believing 

 this is that he finds the first and seventh alveoli larger than the others, 

 a condition that he considers a first beginning of the condition found 

 in the recent genera of the group. But in the photograph of the jaw 

 it is impossible to see this difference in the alveoli. There is the 

 greatest possibility of a mistake ; and it cannot be asserted with any 

 positiveness where the genus belongs. 



" Placoziphins" is established by Van Beneden on the basis of 

 pieces of a skull from the Tertiary deposits at Antwerp (figured in 

 the Osteographie des Cetaces, pi. 27, fig. 11). It is discussed by Abel 

 (Odontocetes du Bolderien, 1905, pp. 85-88), who considers it a near 

 relative of Physcter. In this he is no doubt right, but any final 

 decision is still impossible. 



Hypocetiis was described as a special genus by Moreno (1892, 

 /. c.) under the name Mesocetus Moreno (nee Van Beneden). It was 

 called Hypocctus by Lydekker (1893, /. c, in title and in explanation 

 of plates, Paracetus in text). From Ameghino (Enumeration syn- 

 optique des especes de Mammiferes fossiles de Patagonie, 1894, p. 

 181) it received the name Diaphorocetiis. It is based on a much- 

 broken skull from the Tertiary of Patagonia. Of the genus it can 

 be said that it no doubt belongs to the section Physeterini as a rather 

 near relative of Hoplocetus, but a more exact opinion is scarcely 

 possible. 



