1890.] The Cetacea. 607 
Zygoma interrupted ; symphysis short ; Cogia * Gray. 
aa, Teeth fusiform, with enameled crown. 
Cement coating thick ; Physodon? Gerv. 
aaa, Crown and root of teeth distinct; crown with 
enamel. 
Cement very thick ; Hoplocetus Gerv. 
II. Low jaw with very few teeth. 
a, Maxillary bones with vertical longitudinal crest be- 
hind. 
A tooth at the extremity of each ramus man- 
dibuli ; Anarnacus* Lacep. 
FIG. 4.—Rhabdosteus latiradix Cope (type) ; two-ninths natural size; original; from 
Miocene of Maryland. 1, muzzle from above; ra, do.left side; 2, 24, tooth from side; 
2a. do, 
pas from a different specimen from that represented in the rest of the figures. Teeth 
also separate; two-thirds natural size. 
aa, Maxillary without vertical posterior crests. 
Two aa at the extremity of each mandibular 
Berardius Less. 
Mandibular ramus with a terminal tooth; Chonesiphius Duv. 
‘Mandibular ramus with a median tooth ; Mesoplodon Gerv. 
As already remarked, the extinct sperm whales do not equal 
in dimensions the single recent species. Their teeth differ a good 
deal from those of the latter. Thus the American form, which 
Leidy called Orycterocetus, have the crowns quite slender, and 
the pulp-cavity large. They occur in the Miocene beds from 
* Physeterula Van Ben. 
5 Scaldicetus DuBus [?]; Balenodon Owen. s ödon Lacep. 
