266 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 
There is no vomer developed, but a triangular cartilaginous element 
pendent trom the cranial rostrum affords attachment for the palatine 
element anteriorly; this element is inclined obliquely downwards and 
backwards and is joined to the rostrum by its anterior border. 
The articular condyle for the suspensorium, as already indicated, is a 
discoidal cartilaginous element (resting in a fossa under the lateral ex- 
pansion of the cranium); it has a papilliform eminence in the center, 
which fits into a conical depression in the head of the slender hyoman- 
dibular bone; the hyomandibular, and especially the quadrate, are ex- 
cessively elongated and articulate by an intermediary cylindroidal car- 
tilaginous bond, which reminds one of the intervertebral disks seen in 
the spinal column of mammals; this cartilage is ensheathed behind by 
a splint-like prolongation of the quadrate, which is prolonged and at- 
tenuated on the surface of the hyomandibular; the distal end of the 
quadrate is grooved longitudinally, forming, with the articular end of 
the mandible, a complete ginglymus joint. 
The vertebre are very numerous, and at the same time very simple 
and little differentiated from each other. 
The vertebral centra are annular, and constricted in the middle like 
a dice-box, and the cavity of each vertebra is filled with vacuolated 
tissue, the remains of the chorda; the centra are connected together 
by cartilaginous annular ligaments. 
The neurapophyses are slender, diverging (instead of convergent), car- 
tilaginous distally, and embracing the neural sheaths on the sides, while 
by the neurapophyses is supported a membranous sheath which roofs 
over the nervous chord, and around which there is a wide serous space 
which extends into the cranium, expanding so that the serous space 
around the brain is as capacious relatively as, or more so than, in Elas- 
mobranchs. 
Hemapophyses are represented by parallel plates on the ventral face 
of the centra, and these plates are broadest at the ends of the vertebra. 
The first vertebra is shorter than those which follow, and the caudal 
vertebre are simpler than those of the body and prebranchial region ; 
at the extreme tip of the tail there are possibly no vertebra differen- 
tiated, the skeletal axis of the body being represented by the notochord 
and its sheath. 
The interspinous basalia of the median fin rays are composed of two 
pieces, one proximal, the other distal, with the articular extremities 
represented by cartilage. 
The median fin rays at their base have cartilaginous articular por- 
tions mesially divided, the halves continued distally into the lateral 
halves of the unsegmented rays. The medulla or axial portion of the 
rays is not cartilaginous. 
There is an eradiate ventral fold of ectoblast, as in embryo fishes. 
No dorsal or anal rays exist for some distance from the end of the tail. 
(These last are features which would indicate a defective development 
of the extreme caudal end of the bony skeletal axis of the body.) 
