52 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. 62, 
lachrymal is a small wedgelike bone which fills the interval between 
the posterior margin of the ventral plate of the maxilla and the 
supraorbital plate of the frontal. 
PERIOTIC. 
The right periotic (pl. 8, figs. 5-6) of Squalodon calvertensis differs 
considerably from that of Hurhinodelphis longirostris™® and possesses 
many of the structural peculiarities exhibited by those of Delphinodon 
dividum™ and Prosqualodon australis.”* The bone may be described 
as irregularly triangular. The posterior end, or mastoid process of 
petrosal, is short and stout, while the anterior end of the petrosal 
resembles a twisted cone. On the ventral face of the anterior process 
Fic. 1—DORSAL VIEW OF RIGHT PERIOTIC OF SQUALODON CALVERTENSIS, NEW 
SPECIES. X2. No. 10484, U.S.N.M.; CALVERT CLIFFS, MARYLAND. THE SAME 
NUMBERS ARE USED IN FIGURES 1 TO 3 FOR THE FOLLOWING PARTS: 1, FENESTRA 
ROTUNDUM; 2, FENESTRA OVALIS; 3, EXTERNAL APERTURE OF AQUAEDUCTUS 
COCHLEAE; 4, EXTERNAL APERTURE OF AQUAEDUCTUS VESTIBULI; 5, PROCESSUS 
ANTERIOR PETROSI; 6, PIT FOR HEAD OF MALLEUS; 7, TYMPANIC APERTURE OF 
FACIAL CANAL; 8, SEMICLOSED CANAL FOR FACIAL NERVE, WITH GROOVE FOR 
STAPEDIAL MUSCLE; 9, PROCESSUS POSTERIOR PETROSI (MASTOID PROCESS, IN PART); 
10, INTERNAL ACOUSTIC MEATUS; 11, FORAMAN CENTRALE; 12, FORAMEN SINGU- 
LARE; 13, INTERNAL OR CEREBRAL APERTURE OF FACIAL CANAL. 
of the petrosal there is a circular depression in which the head of the 
malleus is lodged. The malleus, presumably, was united with the 
tympanic and situated anterior to the caudal lip of the bulla. The 
mastoid process of the petrosal fits loosely into a notch on the squa- 
mosal, yet the contact shows that correct relations were maintained 
with the open channel for the external auditory meatus. The anterior 
face of this process is hollowed out. The pedicle on the posterior 
end of the tympanic rests on the flattened and rectangular ventral 
face of the mastoid process of the petrosal. 
A thin ledge is formed by the internal prolongation of the inferior 
margin of the mastoid process of tbe petrosal which partially roofs 
76 Abel, O., Méin. Mus. Roy. Hist. Nat. Belgique, Bruxelles, vol. 2, fig. 19, p. 122, 1902. 
7True, F. W., Journ. Acad. Nat. Sci. Philadelphia, ser. 2, vol. 15, p. 175, pl. 25, figs. 6-11, 1912. 
78True, F. W., Smithson. Misc. Coll. (Quart. Is.), vol. 52, pt. 4, Publ. 1875, fig. 78, p. 452, 1909. 
