42 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76 



cetus, Palccodclphis, Patriocctus', Phocanopsis, Phocagcnius, Physo- 

 don, Prise odelphinus, Prophysetef, Prosqualodon, Protophoccena, 

 Rhabdostciis, Scaldicetus, Stcnodofi, Tretosphys. 



Most of the supergeneric groups here recognized have already 

 been sufficiently discussed for the purposes of this paper. Concern- 

 ing some of them further observations may not be out of place. 



Arcliccoccti. — Cabrera (Manual de Mastozoologia, p. 316, 1922) 

 has recently placed the zeuglodonts in an order separate from the 

 modern cetacea. This may be the first step toward the eventual ele- 

 vation of all three of the currently recognized major groups to the 

 rank of orders. 



According to Pompeckj (Senckenbergiana, Vol. 4, pp. 43-100, Oc- 

 tober 20, 1922) the structure of the periotic bone in the zeuglodonts 

 resembles that now found in the baleen whales. The presence of 

 such conditions is not likely to mean anything more than a parallel 

 development of the ear in the two groups, or more probably, the 

 existence of similar ear structure in the two ancestral stocks from 

 which these groups took their origin. The difficulties in the way of 

 deriving a mysticete skull from one which had first assumed the form 

 present in all known zeuglodonts appear to be little short of in- 

 superable. 



A g or o phiidcc— 'The three American genera now placed in this fam- 

 ily are well dififerentiated from each other though they probably 

 represent one stage of the telescoping process. Whether the genus 

 Patriocetus belongs in the same family or whether it represents a 

 distinct group are questions which the descriptions and figures do 

 not furnish the data for answering. The photographs published by 

 Abel (Denkschr. kais. Akad. Wissensch. Wien, math.-naturw. Kl., 

 Vol. 90, pis. 1-4, 1914) indicate (a) that the general form of the 

 skull in both dorsal and lateral view is essentially like that of Agoro- 

 phius (Smithsonian Inst., Special Publ., No. 1694, pi. 6, 1907), and 

 Archao del phis (Bull. Mus. Comp. Zool., Vol. 65, No. i, figs, i, 2 and 

 plate, 1921), (b) that the braincase is similarly small as compared 

 with the rest of the skull, and (c) that a deep postorbital constriction 

 is present. Apparently the maxillary may have formed part of the 

 anterior orbital wall as in Arehceodelphis. The most obvious differ- 

 ence from Agorophius clearly shown by Abel's photographs is the 

 presence of a thin overhanging ledge sloping upward and backward 

 from the hinder margin of the orbit, and partly obscuring the post- 

 orbital constriction. The surface of the fossil is thickly covered with 

 grains of sand which obscure most of the finer details. (See remarks 



