74 ME. J. W. KIRXBY OJS T PERMIAN FISH AND PLANTS. 



irregularly placed, and occasionally slightly bent towards the 

 point, and appear to have a few minute teeth between them. 

 The surface of the lower jaw is covered with a pustulate and 

 wrinkled ornamentation ; the surface of the rest of the bones of 

 the head, including the opercular plates, has also a rugulose 

 appearance. In one specimen there appear to be traces of branch- 

 iostegal rays. 



The scales are small and rhomboidal, varying, however, con- 

 siderably both in size and form. The dorso-ventral series are 

 arranged in steeply sloping curves. The lateral thoracic scales 

 are much larger than those of the dorsal, ventral, and caudal 

 regions, being three times the size of some of the latter ; these 

 scales (lateral thoracic), by their great relative width and greater 

 amount of overlap, appear more rectangular in outline than those 

 of other parts of the body. The scales of the ventral region are 

 much the smallest. These latter, and the scales of the caudal 

 portion of the body are those which, by form and ornament, are 

 the most typical of the genus as established by Agassiz. The 

 scales of the thoracic part of the body articulate by means of 

 long, sharply pointed projections from the superior margin, which 

 fit into sockets or depressions of the reverse and inferior portion 

 of the overlapping scale above, as in Palceoniscus and so many 

 other of the Lepidoidei. This system of articulation becomes 

 obsolete towards the caudal extremity. The scales of the thoracic 

 region, especially the ventral ones, overlap each other more than 

 those of the caudal region. All these scales are thick and finely 

 enamelled, and are ornamented with two or more converging- 

 furrows, which always terminate within the margin. Besides 

 the scales noticed, there are series of large, oval, pointed, bluntly 

 lanceolate, and lanceolate scales, placed in advance of the dorsal, 

 anal, and each lobe of the caudal fins. These scales, which 

 Agassiz terms the grosses ecailles impaires, attain the length 

 of one-third of an inch, and number in each series from four 

 to six ; and they would appear to pass by gradations into the 

 long pointed fulcral scales or spines that fringe the fins. The 

 surface of these scales is closely covered with a similar ornamen- 

 tation to the other scales, though more elaborate than it. 



