2 



BRITISH FOSSILS. 



orbit is of moderate size, and placed in a forward position. The 

 snout is thickened and rounded at its extremity. The mouth is 

 large, and capable apparently of great distention. The operculum is 

 quadrilateral, and the sub-operculum triangular. The line of junction 

 between them runs obliquely upwards and backwards The pos- 

 terior border of these bones is nearly perpendicular. All the cranial 

 bones and their appendages are highly ornamented by deep grooves, 

 arranged in a variety of elegant patterns. On the upper part of the 

 head they are grouped longitudinally, running in sinuous, and 

 sometimes inosculating lines, from the occiput to the snout. On 

 either side the latter, they are retroflexed with a sigmoid curve, 

 exactly resembling the common tattoe pattern on the alee of a New 

 Zealander's nose. On the premaxillary bone the}^ are parallel to its 

 lower margin, and on the lower jaw they run obliquely downwards 

 and backwards. The opercular bones are less deeply sculptured, 

 and the furrows are more distant. On the posterior angles they 

 become almost obsolete. The scales (with the exception of a few 

 immediately behind the thoracic arch) (Plate viii. lig. 2.) are long and 

 narrow. The base of each is marked by three or four distinct bars. 

 The surface of each scale behind the base is cut by two (or sometimes 

 more) grooves, always varying in length, but rarely extending to 

 the posterior edge of the scale, which is deeply notched. They are 

 all incrusted with a thick and lustrous coat of ganoine. The an- 

 terior insertion of the dorsal fin is equidistant from the nose and 

 the commencement of the tail. The fin itself is moderately long, 

 and contains 22 rays. Of these the sixth and seventh from the 

 front seem to be the longest. The transverse articulations of the 

 rays are very frequent near the base, but become more and more 

 distant. After the fourth articulation the rays are grooved, but 

 they do not dichotomise, so far as the fin is preserved in the specimen. 

 It is devoid of fulcral scales. The base of the pectoral fin is all that 

 remains of this organ. The anterior rays are disproportionately 

 strong. The ventral fins are deficient, but they seem from the 

 impression on the shale to have been small. They are inserted 

 below the hinder part of the dorsal fin. The anal fin is small, and 

 very distal in position. Its hinder rays almost reach the tail. The 

 latter is of moderate size, and forked. It has a strong fringe of 

 oblique rays along its upper margin, and a similar one, though 

 finer, protects the lower edge. A few of the terminal vertebrae 

 of the column are preserved. They diminish gradually in size, 

 and terminate at the commencement of the upper lobe of the 

 caudal fin. 



