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Show 1897.J ECHIONOCEPHALUS, A HALOSAUROID FISH. 269 quadrate arcade, very slender in front and reaching forwards almost as far as the symphysis of the mandible. The suspensorium is obviously much inclined forwards. The quadrate (ou.) is observed to be small and wedged between the ectopterygoid (ecpt.), entopterygoid (enpt.), and metaptervgoid (mpt.). The mandible (md.) is long, elevated in the middle, and truncated at the symphysis; but although it articulates with the quadrate just behind the middle point of the head, the gape of the mouth seems to have been small, scarcely half the extent of the ramus entering the oral border. A stout marginal bone of the upper jaw is imperfectly shown sloping downwards and backwards from the end of the rostrum to a point just behind the mandibular symphysis, and this m a y be interpreted as premaxilla (pmsc.). The mouth must have been distinctly inferior, the rostrum a little prominent. Behind the skull there is the smooth impression of a relatively small trapezoidal plate, which may be regarded as the operculum (op.); but its antero-superior border is not clearly defined. Adjoining this plate at its anteroinferior margin is another larger plate ornamented with fine, radiating strias, which are evidently directed almost at right angles to its curved posterior and inferior border. This bone exhibits no connection with the mandibular suspensorium, which is considerably further forwards, and its precise shape cannot be determined owing to a crush upon the hyoid arch ; it is evidently the suboperculum (s.op.). Impressions of nine slender and gently curved branchiostegal rays (br.) are shown, and are attached to a remnant probably of the ceratohyal. The vertebras are merely shown in impression, but they are extremely numerous, while the centra are short and deep, each marked by fine longitudinal ridges. The vertebral arches are too delicate to be clearly observed. A delicate, curved, clavicular bone (cl.) occurs behind the opercular apparatus, but there are no traces of the pectoral fins. The remains of the pelvic fins are also too imperfect for description ; but the anterior rays of the short dorsal, slightly further back, are beautifully shown. The foremost ray seems to have been undivided, and is two-thirds as long as the second. This also is not forked, but appears to have been articulated at moderately wide intervals in the distal portion. The third, fourth, aud fifth rays not only exhibit distant articulations, but also bifurcate twice in the distal portion. The hinder rays are imperfect, the bases only of three being preserved. The anal fin-supports are very short in proportion to the length of the rays, and do not interdigitate with the more slender hasmal arches, which are inclined to the axis of the body at a much more acute angle than they. The foremost anal fin-ray is undivided and somewhat shorter than the next. The fifth ray exhibits one bifurcation, but the impressions of the others, so far as distinguishable, are simple. N o scales can be seen. Another specimen (Plate XVIII. fig. 2) displays the trunk especially well in impression, with fragmentary remains of the head. The articular end of the mandible (md.) is shown, with straight inferior border, very low articulation, and the ramus rapidly rising |