12 PROCEEDINGS OF THE NATIONAL MUSEUM. VoL. 62, 
to in«lude certain species of squalodonts having ‘“‘some of the poste- 
rior superior molars three-rooted.” No type species was designated 
and while some may hold that it was Cope’s intention to apply this 
proposed name to Squalodon gervaisw in accordance with a key drawn 
up by him in 1867 * he did not actually do so. The inference drawn 
from his remarks is that he was aware of more than one form having 
three-rooted upper molars. In view of the above facts it seems advis- 
able to select a form which not only possesses such features as will 
fall within the limits of his diagnosis but also one that will best illus- 
trate these peculiarities. Since Pachyodon catulls of Molin best fulfills 
these requirements it is here selected as the type of Trirhizodon Cope 
and may stand as Trirhizodon catullt (Molin). 
MICROZEUGLODON CAUCASICUM (Lydekker). 
Zeuglodon caucasicum LYDEKKER, R., Proc. Zool. Soc. London, pt. 4, No. 38, 
pp. 559-561, pl. 36, figs. 1-3, April 1, 1893. 
Type specumen.—Based upon the posterior portion of a left mandib- 
ular ramus containing four serrate molars, a second fragment of a jaw 
with five broken teeth, a left humerus, and an imperfect caudal verte- 
bra. Loaned to Lydekker by H. Sjégren, of Upsala, Sweden. 
Type locality‘ A Tertiary deposit, in company with a number 
of fish remains, in the Caucasus.’’ This deposit is referable to the 
‘‘ Sumgait-serien ’’ or Kocene according to Hjalmar Sjégren.** Both 
Lydekker ** and Abel ** have questioned this correlation, the former 
suggesting a Miocene age, and the latter an Upper Oligocene age for 
the cetacean remains. 
Subsequent allocation.—Stromer “ was the first to point out the radi- 
cal differences which exist between Zeuglodon caucasicus, so far as rep- 
resented by skeletal remains, and true Zeuglodon. As a result of his 
comparisons he concluded that these remains were not referable to 
any previously described genus and proposed Microzeuglodon. Abel* 
was so impressed by these differences that he erected a new family, 
Microzeuglodontidae, to include this form. At the same time he * 
remarked that there was considerable resemblance between Zeuglodon 
caucasicus Lydekker and the squalodonts Neosqualodon assenzae Dal 
Piaz and Microsqualodon gastaldia (Brandt). Abel remarks that so 
little is known concerning Zeuglodon caucasicus that its relationships 
with Neosqualodon can not be settled, and yet he considers there is 
sufficient data available for the erection of a new family for it. Both 
43 Cope, E. D., Proc. Acad. Nat. Sei. Philadelphia [vol. 19], p. 151, 1867. 
44 Sjégren, H., Meddelandenf ran Upsala Universitets Mineralogisk-Geologiska Institution, Stockholm 
vol. 13, fase. 2-3, p. 4, 1891. 
45Lydekker, R., Proc. Zool. Soc. London, pt. 4, No. 38, p. 559, 1893. 
46 Abel, O., Denkschr. Kais. Akad. Wiss. math,-naturw. K1. Wien, vol. 90, p. 203, 1913. 
47Stromer, E. von, Beitriige z. Palaont. u. Geol. Oester.-Ungarns u. d. Orients, Wien, vol. 15, p. 89 
1903. 
48 Abel, O., Denkschr. Kais. Akad. Wiss. math.-naturw. Kl. Wien, vol. 90, p. 220, 1914. 
4 Ahel, O., Idem, p. 207. 
