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asymphysealsuture. Olfactory organ rudimentary or absent; the nasal 
bones appressed on the frontals and overlapped distally by the meseth- 
moid. 
DENTICETE. 
B. Teeth absorbed and disappearing before birth. Upper jaw provided 
with plates of baleen. Supramaxillary not expanded backwards over 
the frontal bones, but produced outwards in front of the orbits. Rami 
of lower jaw connected by fibrous tissue, and not by suture. Olfactory 
organ distinctly developed; the nasal bones projecting forwards, and 
not overlapped at their distal ends. 
MYSTICETE. 
ZEUGLODONTIA. 
FAMILIES. 
I. Parietal, frontal, and especially nasal bones elongated. Anterior nares 
open forwards. (Cope.) 
BASILOSAURIDAE. (LXIV.) 
Il. Parietal, frontal, and especially nasal bones abbreviated. Anterior nares 
open far behind. (Cope.) Sia anemia 
LXIV. BASILOSAURIDAE. 
Extinct genera. 
Basilosaurus Harl.=Zeuglodon Owen=Pollptychodon Emmons=Hydrarchos Koch. 
Durodon Gibbes=Pontogenus Leidy. 
LXV. CYNORCIDAE. 
Extinct genera. 
ty (Fide Copei.) 
Portheodon Cope. 
Squalodon Grat.=Colophonodon Leidy, Cope, 1867. 
Cynorca Cope. 
Delphinodon Leidy=Squalodon Cope, 1867. 
Genera? incertae sedis. 
Stenodon Van Ben. 
Saurocetus Gibbes. 
DENTICETE. 
FAMILIES. 
I. Rostrum of skull moderately prolonged, and terminating in a rounded or 
subangulated apex. 
A. Head (generally) rostrated and attenuated, or ledge-like around the 
i margin. Skull with the vertex produced forwards. Supraoccipital not 
; projecting forwards laterally above the temporal fossz. Froutals visible 
