496 A. Smith Woodward—On the Genus Synechodus. 
V.—On tHE CreTAcEOoUS SELACHIAN GENUS SYNECHODUS. 
By A. Smita Woopwarp, F.G.S., F.Z.S., 
of the British Museum (Natural History). 
es than forty years ago the detached teeth of Hybodont 
Sharks were recognized by Reuss'in the Cretaceous rocks 
of Bohemia, and these were referred to the genus Hybodus under 
no less than eight specific names. About twenty years later, evidence 
of a somewhat similar Selachian was discovered by Mr. William 
Davies and Mr. 8. J. Mackie, in the Lower Chalk of Kent; and the 
cartilages of the jaw, with a few teeth, were briefly described by 
the last-named geologist” under the name of Hybodus dubrisiensis. 
In 1886, the. present writer pointed out,> from more recently dis- 
covered specimens, that the English Cretaceous species was more 
specialized in every respect than any of the typical forms of 
Hybodus; and quite lately it has been proposed * to regard this 
fossil as generically distinct, with the new name of Synechodus. 
It now appears, indeed, that ‘ Hybodus” dubrisiensis is much 
more nearly related to Palceospinaz than to the typical Hybodus. 
This is well shown by the almost complete dentition of one jaw, 
exhibited in a fine specimen from the Chalk of Sussex, preserved 
in the Willett Collection in the Brighton Museum ; and the oppor- 
tunity of making known this important new fossil—kindly afforded 
by Henry Willett, Esq., and the Chairman of the Museum Committee 
(Edward Crane, Esq.)—seems a fitting occasion for briefly sum- 
marizing our present knowledge of the skeletal and dental characters 
of the fish. All the cartilages are only superficially calcified, but 
the thin hardened layer is comparatively resisting, and it has thus been 
sufficiently preserved in some cases to indicate the precise contour 
of several parts of the skeleton. 
Head.—Nothing worthy of note has been observed in connection 
with the cranium; but the mandibular and hyoid arches are well 
known and of great interest.° A facette upon the superior border 
of the pterygo-quadrate cartilage may almost certainly be regarded 
as indicating a post-orbital articulation with the cranium; and in 
correspondence with this arrangement the hyomandibular element 
is remarkably slender. There is thus considerable resemblance 
between the skull of Synechodus and that of the existing Notidanus ; 
both exhibiting a very primitive condition of the mandibular and 
hyoid arches, and showing a tendency to specialization in one and 
the same direction. 
1 A. E. Reuss, “ Verstein. bohm. Kreideform.,”’ 1845-6, pt. i. p. 2; pt. ii. 
pp- 97, 98, with figs. 
2 §. J. Mackie, “On a new species of Hybodus from the Lower Chalk,’ The 
Geologist, vol. vi. (1863), pp. 241-246, pl. xiii. 
3 Smith Woodward, “On the Relations of the Mandibular and Hyoid Arches in 
a Cretaceous Shark (Hybodus dubrisiensis, Mackie),’’ Proc. Zool. Soc., 1886, 
. 218-224, pl. xx. 
4 Smith Woodward, “ A Synopsis of the Vertebrate Fossils of the English Chalk,”’ 
Proc. Geol. Assoc. vol. x. (1888), p. 288. 
5 See figures in Proc, Zool. Soc. 1886, pl. xx. 
