1866.] YOUNG PLATYSOMIJS. - 313 



accepted on the authority of Sir. P. Egerton, enough has been said 

 to prove, as I think, not only the distinctness of that genus from any 

 of the flat fishes of the Coal, but also that, as yet at least, the family 

 to which it belongs has no true representative in the Carboniferous 

 series. 



Mesolepis, nov. gen. (PI. XXI.) 



Among a number of specimens marked Platysomi, three were found 

 on closer inspection to belong to a new genus. They are charac- 

 terized by the presence of a small ventral fin, a longer anal, and a 

 dorsal which extends from opposite the anterior border of the former 

 to the posterior margin of the latter. The scales are broader in 

 proportion to their height than in Platysomus or AmpJiicentrum, 

 while the lepidopleura, weaker than in those genera, approach 

 somewhat to the kind of articulation present in Amhlypterus and 

 Eurynotus. The imperfection of the head prevents anything being 

 said of it, save that the suprascapular is larger than in the above 

 genera, both it and the operculars rather resembling those of Eury- 

 notus, especially in the presence of concentric growth-lines. For- 

 tunately, however, one specimen shows three teeth, and these are 

 closely similar to those described by Sir P. Egerton in PI. macrurus, 

 presenting a bluntly conical, minie-bullet-shaped crown with a con- 

 stricted neck, much like the Olohulodus of Miinster. 



From the characters of the scales I propose the name Mesolepis 

 for this genus, and give the following definition : — 



Body oval, or arched in the anterior dorsal region, terminating by 

 a blunt prolongation in the upper caudal lobe. Pectoral fin large, 

 its extremity rounded. Ventral small, narrow, at, or slightly in 

 front of, the middle of the body, equidistant between pectoral and anal. 

 Dorsal commencing opposite the ventral, and extending to the tail- 

 root, terminating opposite the posterior margin of the anal, which is 

 rather more than one-half its length. Caudal root strong ; upper 

 lobe larger than lower. The anterior rays of all the fins are the 

 longest, and bifurcated only at their extremities ; the following rays 

 are slender and divided so as to form a delicate fringe. Orbit large, 

 well forward, close to the facial line. Teeth stalked, with a con- 

 stricted neck and smooth bluntly conical crown. Scales quadrila- 

 teral, those on the flanks higher than broad ; the others more equi- 

 lateral. Ornament on them, and on head-bones, tuberculo-linear. 



Two species are distinguished by the following characters : — 



M. Wakdi (PI. xxi. figs. 1, 3). 



Body ovate ; the posterior dorsal slope more rapid than that of 

 the anal region. Length of trunk, from pectoral to tail-root, nearly 

 twice its greatest depth. Caudal root thick, elongate. Scales orna- 

 mented with tubercles, more or less confluent into approximately 

 vertical ridges. 



M. SCALARIS. 



Body more arched dorsally. Tail-peduncle very short and slender. 



VOL. XXII.— PART I. z 



