428 ME. J. W. DAVIS ON A NEW SPECIES OE CCELACANTHES 



constituting the upper surface of the cranium form a compact and closely attached group. 

 Anterior to the frontal hones there is one forming the snout, prohahly the ethmoid (eih), 

 which readies over and more or less envelops the anterior extremities of the rami of the 

 upper jaw. The orbit (orb) is moderately large ; its upper boundary is formed by the frontal 

 and parietal bones : between these and the maxilla the structure of the lateral surface of 

 the head is somewhat obscure. There was an important osseous plate extending from 

 the orbit to the opercula, apparently the temporal bone (t) ; and one or more smaller 

 ossicles filled up the interval between the maxilla, the anterior portion of the orbit, and 

 the bones of the cranium. The opercular bones are three in number ; the operculum 

 (op) was a large bony plate, subtriangular in outline, extending to and overlapping the 

 scapular bones of the pectoral arch. In addition to the operculum there are two other 

 plates, similar in form, but only about one fourth its size : they were probably the sub- 

 operculum (i.op) and interoperculum (s.op), and are represented on PI. XLVII. fig. 1, and 

 also in the l'estoration represented on PL XLIX. 



The upper jaws (mx) are frequently observed in specimens, but in no instance with 

 sufficient certainty and clearness to enable an exact description to be given of their form. 

 They were considerably shorter than the mandibles (M) of the lower jaw, thickest and 

 strongest beneath the orbit ; and, tapering towards the symphysis, the most anterior portion 

 was probably divided by the insertion of the preinaxillaries (PI. XLVII. fig. 11). The 

 mandibles are strong, about 3 inches in length ; the lower margin is straight, and was 

 grooved and smooth where attached to the jugular bones ; the upper margin is anteriorly 

 depressed, but expands towards the median portion to a height of '35 of an inch above the 

 inferior margin ; towards the posterior extremity the surface is again depressed. The pre- 

 sence of teeth in either the maxilla or mandible is somewhat problematical. An exami- 

 nation of many specimens has failed to show an example with teeth in situ. At the same 

 time, a number of teeth are occasionally seen mixed with the bones of the head, and 

 it is possible may have been so loosely attached to the jaws that they have invariably 

 become separated after the death of the fish. The teeth arc about "1 of an inch in 

 length, smooth, slightly curved, and acutely pointed. The whole of the under surface 

 of the head between the two rami of the lower jaws is occupied by the jugular plates (ju): 

 they are large, elliptical in form, internally strengthened by a median process traversing 

 the longitudinal axis of the plate, and externally ornamented by an extremely beautiful 

 arrangement of ridges on the surface of the ganoine, varying much in detail, but running 

 for the most part parallel with its longer axis. 



The scales are moderate in size and rather thin. About one third of the surface of 

 each scale is exposed, the remaining portion being covered by the succeeding scales. 

 The outline of the exposed part forms a parallelogram, the exposed margin forming a 

 more or less acutely pointed angle, whilst the margin hidden by overlapping scales is 

 circular. The scales covering the ventral surface are the largest and broadest : they 

 measure - 3 of an inch across; the length of the scale is - 35 of an inch, of which the 

 exposed surface occupies '2 of an inch. The scales on the sides average the same length 

 as the ventral ones, but are only about 2 of au inch across. The scales decrease in size 

 towards the tail : they do not appear to exhibit any well-defined lateral line ; they run 



