1886.] SQUALORAJA POLYSPONDYLA. 533 
the two excavations at the base of the rostrum in the fragment 
shown in Davies’s fig. 4 evidently testify to their normal proportions 
and situation. Ina line with the prominence is fixed the base of 
the rostral spine (7.s), quite at the hinder extremity of the ethmoi- 
dal tract ; and still more posteriorly, the chondrocranium begins to 
exhibit considerable lateral compression, though finally widening to 
a slightly broader occiput. 
Extending backwards from the antorbital process, the slender 
postpalatine cartilage (pé.pa) is preserved in most specimens 
(especially in no. IV. fig. 2), but there is some uncertainty as to 
whether it formed a distinct element. It tapers slightly to its distal 
end, and the crushing during fossilization has usually imparted to 
it the deceptive appearance of connection with the hyomandibular. 
No postorbital process can be observed, and the circumstances of 
preservation are probably accountable for the absence of any trace 
of a fontanelle in the cranial reof; but there is an interesting 
V-shaped protuberance (a.v) close to the hinder extremity, evi- 
dently representing a fold round the hollow into which opened the 
aqueductus vestibuli (or ductus endolymphaticus) of each auditory sac. 
On the ventral aspect, the parachordal, or “ investing mass” 
(fig. 3, iv.m), is produced posteriorly into a pair of occipital 
condyles (oc.c), as already noted by Riley; and there is a well- 
marked median ridge (x), obviously due to the remains of the 
primitive notochordal sheath. A median foramen (c.f) is also some- 
what conspicuous, and, if not the result of accident during fossiliza- 
tion, is evidently the passage for the united internal carotid arteries 
proceeding to the pituitary body’. 
Of the mandibular and hyoid arches, the hyomandibular cartilage 
(figs. 1, 2, hm) is the only portion satisfactorily preserved. In its 
crushed condition it is seen to extend from each side of the occiput, 
curving outwards and forwards, and gradually tapering to the distal 
extremity. In shape it approximates to that of most “ Batoidei,”’ 
being twice as broad proximaily as distally, and its apparent eonti- 
nuity with the cranial roof is probably due to the process of fossili- 
zation. Not a trace of the pterygo-quadrate and mandibular 
cartilages appears exposed to view; but the arrangement of the 
dental plates in the specimen no. III. (fig. 3, ¢) shows that the two 
rami of the jaw met at the symphysis in a comparatively acute angle, 
and were not placed in the same straight line, as is the case in so 
many living Rays. 
But the most remarkable feature to be noticed in the skull of 
Squalorga is preseuted in the two pairs of transversely elongated 
appendages, with reflected ends, arising from beneath the narrow 
part of the palato-trabecular region. These curions structures are 
not well shown in our fig. 1 (cé.a, ci.6), but can be studied in their 
entirety in the large specimens figured by Riley and Davies. The 
most anterior (ci.a) is the larger, and is completely displayed on 
both sides of the last-named fossil ; its total length is equal to three 
times the width of the skull at the position where it emerges, 
* See T. J. Parker, ‘ Zootomy,’ 1884, p. 62, fig. 20. 
