ART. 16, TWO SQUALODONTS FROM MARYLAND—KELLOGG. 53 
the fallopian or facial canal posteriorly. The tympanic cavity of 
the internal ear of this squalodont periotic is limited externally by 
this crest. The deep and narrow groove which forms the facial canal 
commences on the posterior margin of the periotic and leads to the 
opening for the fallopian tube. The fenestra ovalis lies below this 
canal and on the lateral face of the labyrinthic portion of the periotic. 
The duct passes obliquely upward. The absence of any stapes sug- 
gests that it was not firmly fixed as in some of the whalebone whales. 
Perhaps an annular ligament held the stapes in place since it did not 
completely fill the fenestra ovalis with its foot plate. 
The inferior half of the central portion of the periotic corresponds 
to the labyrinthic region. On the posterior end of this structure there 
is asemicircular opening, the fenestra rotundum. A rounded promon- 
tory is formed above this opening by the closure of an open 
groove, which, at some time during this cetacean’s growth, extended 
across the posterior face of the 
labyrinthic and opened on the 
internal face. This groove 
represents the common open- 
ing of the fenestra rotundum 
and the external aperture of 
the aquaeductus cochleae. A 
small canal connecting the fe- 
nestra rotundum with the ex- 
ternal aperture of the aquae- 
ductus cochleae remains open. - 
The apertures for the facial FG. 2.—PosTERIOR VIEW OF RIGHT PERIOTIC OF SQUA- 
0 LODON CALVERTENSIS, NEW SPECIES. X2. No, 10484, 
canal, fenestra ovalis, fenestra U,S.N. M.; CALVERT CLIFFS, MARYLAND, 
rotundum, and the external 
aperture of the aquaeductus cochleae, as well as the course of 
the facial canal are practically identical in position with those of 
Delphinodon. 
On the dorsal face and near the posterior margin is a partially 
closed suture which presumably marks the line of contact between 
the mastoid and the labyrinthic portions of the periotic. 
The most noticeable feature of the internal face is a large elliptical 
opening, the roof of which defines the limits of the labyrinthic and 
petrous portions of the periotic. Within this opening a thin bony 
partition separates the aperture for the facial canal from a deep and 
more centrally placed fossa. This fossa represents the internal acous- 
tic meatus which receives the acoustic nerve and the internal audi- 
tory artery. At the bottom of this fossa is the tractus spiralis 
foraminosus, but this structure is barely visible. A small foramen is 
present at the top of the previously discussed bony partition and 
leads into the vestibular portion of the periotic. This could trans- 
