44 
PROCEEDINGS OF THE NATIONAL MUSEUM. vou. 62, 
c'. Molars united throughout their length by a thin isthmus, and two rooted. 
Five to six pairs of two-rooted mandibular teeth. Rostrum broad at 
base and very short. External nasal openings situated posterior to the 
maxillary notches. Maxillary notches narrow in consequence of the 
conspicuous antero-external projection of the maxillae as in physeter- 
ine whales. Nasals triangular in shape and partially roof over nasal 
apertures. Mesethmoid forms the thick partition separating the nasal 
passages externally, provides support for the abbreviated nasals, and 
sheathes dorsal and lateral faces of the presphenoid which in turn forms 
the plug across proximal end of mesorostral channel. Mesorostral chan- 
nel open. Supraorbital process of frontal broad, expanded laterally. 
Supraoccipital narrow, equaling about one-half of greatest width of skull 
across the squamosals, emarginate superiorly. Parietals forming a narrow 
strip across the vertex. Premaxillaries bounding the nasals laterally, 
but not extending posteriad to them, and overlapping frontals on vertex 
toaslight extent. Zygomatic portion of squamosals bluntly truncated 
anteriorly. Maxillaries extending posteriad beyond tips of premaxil- 
laries and in contact with parietals on vertex. Mandibular symphysis 
shorter than in Squalodon. Mandible short and laterally curved. Atlas 
is long anteroposteriorly with two superimposed transverse processes on 
either side, and possesses a stout median postero-inferior process for 
edontoid (Patagonia) iNest we ee ote Ne oe Prosqualodon australis 
C?, Molars constricted below enamel crown. Anterior and posterior cutting 
Di, 
d', 
1D: 
edges serrated by accessory cusps. Parietals separate the frontals from 
the supraoccipital by a wide interval on vertex of skull. 
PATRIOCETIDAE. 
Skull with reduced or no intertemporal constriction. 
Crowns of molars low; cusps on posterior edges large, with bluntly rounded 
apices. Roots of molars not united by a thin isthmus, widely diver- 
gent basally. Crowns of incisors compressed and curved inward, their 
anterior and posterior cutting edges sharp. Enamel surface of molar 
clown ornamented with coarse striae. 
Maxillae narrowly overlapping frontals mesally with splintlike ascend- 
ing processes, and not extending posteriad to anterior margins of tem- 
poral fossae. Rostrum broad at base, and relatively short. Maxillary 
notches wanting. External nasal openings situated more anteriorly 
than in Squalodon. Supraorbital processes of frontal broad, expanded 
laterally. Premaxillaries bounding nasals laterally, overriding fron- 
tals mesally, and extending posteriad as far as anterior margins of 
parietals on vertex. Parietals forming a broad strip across the vertex. 
Supraoccipital narrow, equaling less than one-half greatest width of 
skull across squamosals, truncate superiorly. Zygomatic portion of 
squamosal tapering anteriorly. Mesorostral channel wide open. Oc- 
cipital condyles large, their posterior margins produced beyond over- 
hanging edges of temporal fossae (Austria)..Patriocetus grateloupii. 
Patriocetus denggi. 
AGOROPHIIDAE. 
Skull with a distinct intertemporal constriction. 
Crowns of molars high, triangular in outline; cusps on cutting edges small. 
Roots of molars united by a thin isthmus. Enamel surface of molar 
crown lightly sculptured. 
