40 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. 
C'. Molars (so far as known) with two roots. 
D'. Accessory cusps present on both anterior and posterior cutting surfaces 
of some of the molars. 
E'. Crowns of premolars not strongly compressed and provided with one 
crenulate cutting edge (so far as known). 
e1. Molars constricted below enamel crown. 
j'. Roots of molars united at base by a thin isthmus. Posterior cutting 
edge of at least one molar with five to six accessory cusps (Australia). 
Metasqualodon harwoodi. 
e?. Molars not constricted below enamel crown. 
ji. Roots of molars divergent basally, not united by a thin isthmus. 
Posterior cutting edges of molars with four accessory cusps. 
g'. Accessory cusps on cutting edges of molars distinct, and projecting 
freely CAMISHTAIA ese hee e ca eee ee ee Seen serratus. 
g?. Accessory cusps on puta pees of ote cab more closely approxi- 
mating each other. Three or more of the molars in the mandi- 
ble serrated by accessory cusps on both anterior and posterior 
cutting edges. Roots of molars short, converging distally and 
but slightly longer than height of crown (Malta). 
Squalodon melitensis. 
/*. Roots of molars united by a thin isthmus for a considerable portion 
of their length and never widely separated; tips recurved. Roots 
of molariform teeth nearly twice the height of crown. Premolar 
with crenulate cutting edge. Enamel surface of molar crown 
ornamented with coarse anastomosing striae (Australia). 
Parasqualodon wilkinsont. 
I. LoncG-BEAKED GROUP. 
Frontals in contact posteriorly with supraoccipital. Parictals excluded from vertex 
of skull. 
E?, Crowns of premolars strongly compressed, incurved, and provided with 
sawlike cutting surfaces on both edges. Enamel surface of molar 
crown ornamented with striae. 
Rostrum elongated, equaling nearly twice the length of that portion 
of the skull posterior to maxillary notches. External nasal open- 
ings situated far posteriorly. Brain case telescoped. No inter- 
temporal constriction. Supraorbital process of frontal expanded 
laterally, constricted proximally. Frontals in contact posteriorly 
with supraoccipital, and receive the ascending processes of pre- 
maxillae in paired grooves along the internal margins of maxillae. 
Nasals abbreviated, apparently synostosing with the frontals in 
old adults. Mesorostral channel open. Mesethmoid fills large 
frontal fontanelle; forms the thick partition separating the nasal 
passages externally: provides support for the abbreviated nasals; 
and is pierced by a second pair of passages, the foramina for the 
nasal or ophthalmic branches of the trigeminal nerve. Cheek 
teeth increased above the typical number 44; variable 58 to 60. 
Molars not exceeding seven and premolars five in either jaw. 
SQuaALODON 
F'. Both edges of some of the molars provided with sawlike cutting sur- 
faces in addition to the accessory cusps. , 
J}. At least five of the molars in each upper jaw with anterior and pos- 
terior cutting edges serrated by well-defined accessory cusps. 
Roots of molars connected near the base by a short thin isthmus. 
