FROM LYME REGIS. 245 
A yery strong and irregularly, shaped, bone arises from the 
centre of the mass, and, with its base apparently resting up- 
on this bone, is placed. the curred. spine which constitutes 
the principal feature of imterest im the present, specimen. — 
From the, position which this. spine now occupies, it would 
appear, to. have, been situated about, the region, of the head, 
bending abruptly forwards directly, it.emerged from the in- 
teguments. ,.‘Vhe. apex of ;the, spine, is unfortunately, broken 
off; but. the portion left is about half an/inchlong, covered 
witha smooth, glistening coat of enamel, and presenting a 
slight but well-defined, upper edge. .A few elevated and wa- 
vy sinte, are. irregularly distributed upon. its surface. ,, The 
spine arises. from a strong, expanded, bony, base, which. 1s 
formed by three obtuse, processes united in a. common centre, 
one of them, extending anteriorly in:the median Jine, and the 
other two, which may be termed the lateral processes; at right 
angles, tothe anterior one.;,; Some portions . of the surfaces of 
these processes, sould appear to,have given: -attachment to 
very, strong muscles, (fig...7;& 8). 
At the, first glance this hooked spine might be. ‘thought to 
be xelated to those which characterise so, many;species of the 
genus Raia of .Linneus, but,its;remarkable bony base, and 
the general aspect of the organ. itself, would seem to indicate 
its. connexion with,more; important “functions | than ‘are; Pos- 
sessed by,a mere germnah prickle., In, the absence of evidence 
to the contrary,, 1 should feel disposed to, regard it_as a soli- 
tary spine, developed inthe median line of the frontal region, 
and connected swith,or.simply,resting upon the. bones. of the 
cranium. In the Chimera,monstrosa, to which Hy ybo 
some, affinity, a horn or frontal process is also present. In this 
instance; howeyer,,it.is only found in the male, sex, ‘end ‘the 
process, itself has.none, of the. formidable character about it 
presented by the )spine, of Hybodus ; haying but a. compara- 
tively slight base,/and though the apex is armed with a‘ series 
of small. prickles;, the process, itself is, I believe, externally 
fleshy; with an.internal,slight,, bony, support, ‘The apparent 
analogy, howeyer, is worth a passing notice, because. the teeth 
of Chimera;.although, an.existing genus, haye, been found fos- 
sil in deposits which also, contain the remains of Hybodus. 
The. teeth inthe, present specimen. vary from half an inch 
to three ,quarters ofan, inch,in width. They are slightly 
bowed, with the convexity, outwards; and at the same time 
arched from above to below, so that the apices of the outer- 
most lateral lobes, in many instances, are nearly on the same 
level with the base of the central process. The crown of the 
tooth, slightly projects beyond the osseous root which con- 
