310 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Feb. 21, 



and contrast very strongly in shape and size with it. The suboper- 

 cular is the largest of the three bones ; the opercular and interoper- 

 cular are nearly equal ; the latter overlaps the branchiostegals, which 

 are nevertheless enamelled externally. The suprascapular is well 

 developed ; the pectoral arch very strong, the so-called coracoid ex- 

 panding into a wide oval process. The pectoral fins are higher than 

 usual above the ventral margin ; but, relatively to the opercular 

 bones, they hold the same place as in the majority of the rhombic 

 fish, namely, opposite the inferior margin of the subopercular. 



The peaks into which both margins of the body are produced are 

 not opposite : the dorsal being slightly in advance of the ventral. 

 They are formed by a set of gradually narrowing scales, seemmgly 

 denser than the rest, and ending in tolerably sharp recurved points. 

 From these the posterior slopes are rapid, with feebly convex out- 

 lines, the anterior more gradual, straight. The scales are very high 

 in proportion to their breadth on the fianks, and diminish both to- 

 wards the margins and the tail ; never, however, becoming equilateral, 

 save on the upper caudal lobe. The series are nearly vertical, thus 

 leaving, anteriorly to that row skirting the opercular bones, a tri- 

 angular space, whose upper boundary is the mandible. In this area 

 the scales are smaller, but longer than broad, and radiate from the 

 upper posterior corner of the space to the margin of the body. The 

 ornament consists of a thick ganoin layer, raised into partly confluent 

 tubercles, after the fashion of PI. XX. fig. 5. In only one specimen 

 is the evidence distinct of a modification of the marginal scales ; in 

 it those of the ventral edge anterior to the peak have their lower 

 ends denticulate, but as those denticles are attached to high scales, 

 there is no single row, those of opposite surfaces alike contributing 

 to the outline of the trunk. The lepidopleura are very strong, and 

 are of the structure already so well described by Sir P. Egerton {loc. 

 cit.). The fins are made up of rays, slender for the bulk of the 

 animal ; the articles are short, and covered with ornamented scales. 

 They bifurcate successively near their Extremities into a fine fringe. 

 The anterior rays of the dorsal and anal are longer than the rest, as 

 in Platysomus. The anterior rays in all the fins (except the pecto- 

 rals, whose defective state leaves this point undecided) are fringed 

 with a fine series of fulcral scales. Those on the upper caudal lobe 

 are a single row of strong, triangular, peaked scales, with a notched 

 posterior margin. The lateral line is straight, and passes obliquely 

 upwards from the tail to the lower opercular margin. 



Of the internal skeleton little can be said, save that the processes 

 are well ossified, and their vertebral ends expanded so as to approach 

 the half vertebrse of the Pycnodonts. The pelvic bones figured by 

 Agassiz have not been preserved in any specimens I have seen ; and 

 as they are placed by him in front of the anal fin, it seems likely 

 that they are in reality suggested by the frequent distortions of the 

 dorso-ventral scale-rows in that region. 



Fragments of this genus are frequent in the North Staff'ordshire 

 coal-fields : they also occur, though more sparingly, in the Scottish 

 coal-fields, especially in that of Lanarkshire. 



