ENCHODONTIDJE. 
215 
absent only in the area apparently overlapped by the 
upper jaw. The course of the sensory canal on the 
angular and dentary is marked by a deep open groove. 
The preoperculum is narrow and deep, with the long axis 
vertical; and its finely tuberculated lower end is scarcely 
bent forwards, being produced instead backwards into a 
short blunt spine, which is incomplete at the point in the 
fossil. Comparatively slender and well-spaced branchio- 
stegal rays are shown beneath the hinder end of the 
mandible, perhaps eight or nine in number. The vertebral 
centra are much constricted, apparently strengthened 
only by. one ridge on each side, with which the somewhat 
expanded head of the rib articulates. The neural arches 
are small and low laminar expansions, each extending 
along the anterior half of a centrum and bearing at its 
postero-superior angle the long and slender neural spine. 
The imperfect remains of the clavicle exhibit a large inner 
lamina nearly at right-angles to the more delicate lamina 
in the plane of the fiank; and the pectoral fin is shown 
to be relatively large, with at least 12 stout rays, which 
are partly ornamented. The pelvic fins are also indicated 
as stout and far forwards, with antero-posteriorly elongated 
triangular supports. The anterior rays of the dorsal fin 
are shown to be very stout, ornamented with fine tubercu- 
lations and longitudinal rugae ; all are imperfect distally, 
but the foremost is shown to be articulated towards the 
end, while the second and doubtless the others are both 
articulated and divided distally. Purchased., 1857. 
49111. Fra gment of head and abdominal region, displaying the 
characteristic opercular apparatus; probably from the 
Lower Chalk, Burham. Mrs. SmitKs Coll. 
P. 1703 d. Fragment of head and abdominal region; Chalk, Kent. 
The ribs are shown to be compressed, not round in 
section ; and the vertebral centra appear to have been 
pierced by the notochord. Egerton Coll. 
?. 3657. Head and fragment of abdominal region; English Chalk. 
The greater portion of the cranial roof is displayed, and 
the small posterior spine of the supraoccipital bone is con¬ 
spicuous. In side view the maxilla is well exposed, being 
imperfect only at its hinder end. It is shown to be a 
slender bone, slightly deepened in front and curved 
