THE NORTHERN RIBBON-FISH. 4 
above or outside with the frontal, and in front with the mesethmoid. It is much 
smaller than in Regalecus. 
Fig. 3. THe PARASPHENOID. 
The parasphenord, as regards its remarkable displacement (as in Regalecus) far 
below the level of the basis cranz, has already been referred to in general terms. 
Tt is a long bone, straighter than in Regalecus, keeled below, receiving in front the 
pointed posterior end of the vomer beneath the pre-nasal cartilage, and appearing to 
a very slight extent in the posterior view of the skull, beneath the basi-occipital. 
In this latter region it does not present the strong ventral keel seen in Regalecus. 
Posteriorly the parasphenoid comes into relation with numerous bones. On the 
upper surface in the middle line is a prominent median ridge, which is received 
between the descending processes of the basi-occipital, which fit into grooves on 
either side of the said ridge. The anterior ends of the ridge and groove likewise 
articulate with the descending process of each prootic. The sides of the para- 
sphenoid are raised into two outstanding processes, which take their origin opposite 
the anterior end of the ridge. These meet corresponding processes of the sphenotics 
and form the post-orbital pillars. Each is supported by coming into relation with 
the border of the prootic. Lastly, between these post-orbital processes, the ridge’ 
is replaced by a groove in which rests the basi-sphenoid. 
The vomer is a hollow wedge, with thin bony walls, within which fits the pre-nasal 
cartilage ; the latter is further clamped there by two ascending wings, which run 
upwards to articulate with the parethmoids. The lower surface of the vomer is 
keeled, and passes backwards into a deep excavation in front of the parasphenoid. 
The inferior keel of the vomer bears anteriorly three teeth, two large and a smaller 
one between. 
The mesethmord is a shield-shaped bone interposed between the great cartilage 
of the tegmen cram and the pre-nasal cartilage (Pl. 1., Fig. 3), and forming the 
anterior part of the groove for the pre-maxillary processes. It is much larger 
than in Regalecus, and articulates anteriorly and laterally with the parethmoids, 
posteriorly, to a small extent, with the frontals. Below it is somewhat keeled, and 
behind articulates with the orbito-sphenoids. In front it is excavated to form a 
small hollow pit,.the mesonasal cavity (cf. PARKER, loc. cit. ). 
The parethmoids are flat bones, sculptured deeply above and very slightly 
below, to a great extent superficial. Each present a notch on the upper border, 
which is made into a foramen by the anterior process of the mesethmoid, and 
transmits the first division of the fifth nerve. Anteriorly it articulates with the 
vomer, posteriorly with the frontal, internally with the mesethmoid. 
