Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/866

 Kupferschiefer of Richelsdorf and the Eisleben district, where it appears to be very rare.

Dorypterus is pretty regularly oval in contour, inclining to ovate, the posterior slopes being more rapid than the anterior, and the head rather obtuse. It was probably much compressed, and is very deep in proportion to its length ; the length of the body, including the central rays of the tail, is about twice its depth at the deepest part. Our largest specimen is 5 inches long, including the tail, and 2-1/4 inches deep ; and the head, from the anterior extremity of the mandible to the posterior angle of the gill-plate, is about one- third the length of the entire animal, including the centre rays of the tail. The muzzle is obtuse, the mouth shutting upwards ; the mandibles are long, flat, and rather wide ; the praemaxillae are about half the length of the mandibles, and, like them, are flattened and wide ; the maxillae are about as long as the praemaxillae, and bend downwards, and overlap the posterior portions of the mandibles. The gape was large; and the jaws probably shot out a little when in action ; no teeth have been observed.

The orbits (Pl. XLII. fig. 1, u) are large, and are situated immediately behind the praemaxillae and a little below the brow or dorsal ridge ; the gill-plate or operculum (s) seems to be composed of two pieces, and is of a narrow crescent-form, the posterior margin being a little angulated, the angle projecting above the middle longitudinal line of the body. The praeoperculum (t) partakes of the same form, but is considerably less than the operculum, and is placed about midway between the eye and the posterior margin of the gill-plate.

The clavicle (r), which is well preserved in one of the specimens, is a long, stout, fusiform bone, extending from above the longitudinal middle line of the body to the insertion of the ventral fin, and is well inclined thence upwards and backwards.

The pectoral fins (c), which are 8/10 inch long, are wide and somewhat rounded, the extremity being obtuse ; they are rather large in proportion to the size of the body, and are situated just behind and below the angle of the operculum, consequently on the central longitudinal line. They are connected with the upper portion of the clavicle. The remains of apparently the scapula and coracoid were observed in one of the specimens ; they are, however, in a crushed state, but seem to have been broad, flat, and short, and are arched towards each other. From these extend fourteen or fifteen flat and rather delicate brachial rays (c'), the longest of which are near the middle and measure rather more than 1/8 inch in length ; they are articulated with double their number of simple fin-rays, which are composed of numerous joints.

The ventral fins (d) originate in front of the ventral or thoracic plates, to be shortly described, and immediately behind the lower extremity of the clavicle, and incline backwards ; they are upwards of half an inch in length, are proportionally narrow and are sharp-pointed ; they have each about fourteen or fifteen rays, which are made up of numerous joints, and are attached to elongated narrow pelvic bones; but these are too much obscured to admit of complete description.