new Species o/'Semionotus. 177 



the antero-inferior angle slightly produced downwards, and 

 the postero-superior somewhat rounded ; but the upper two 

 thirds of the anterior border were evidently considerably over- 

 lapped, leaving the exposed portion of the bone broader below 

 than above. The outer enamelled surface is merely covere 

 with scattered pittings and exhibits no ornamentation. 



Of i\\e. paired fins, the pectorals (fig. 1) are long and power- 

 ful, but the pel vies are almost, if not quite, undistinguishable. 

 The latter are always more or less rudimentary in Semionotus, 

 but they seem to have been unusually small in the species 

 now under consideration. Each pectoral fin consists of about 

 ten robust rays, undivided for more than a third of their 

 length, then becoming articulated and soon branching. 



In the median fins the rays are similar to those of the 

 pectoral just described — robust, proximally undivided, distally 

 articulated and branching. The dorsal (fig. 1) is unfortu- 

 nately mutilated, but there are traces of the double series of 

 anterior fulcra, followed by about fourteen rays ; and the fin 

 is seen to commence in the middle of the back. The anal 

 (fig. 1) commences at a point opposite the posterior end of 

 the dorsal, and is preceded by two prominent and other 

 smaller fulcra ; it is, as usual, of small extent, but composed 

 of rays of considerable length. The caudal fin is best dis- 

 played in the fragment shown in fig. 7, though its connexions 

 are also seen in two of the other specimens. The extremity 

 of the body is slightly produced upwards — a kind of semi- 

 heterocercy — and the ridge-scales are continued behind as 

 fulcra 5 the rays, however, are so disposed as to produce a 

 completely symmetrical fin, and this is not forked, but some- 

 what rounded, the median rays extending beyond those above 

 and below. 



The scales are thick and covered externally with a smooth 

 shining layer of ganoine. They are of rhomboidal form, 

 varying slightly in different parts of the body, being deepest 

 on the flanks (figs. 1, 8), and most oblique in the caudal 

 region, while those of the ventral aspect (fig. 9) exhibit, to 

 some extent, the elongation characteristic of genera like 

 Eugnathus, &c. With one or two exceptions on the middle of 

 the flank, none of the scales show the slightest trace of denti- 

 culations on the hinder edge. None, moreover, appear to be 

 united by " peg-and- socket " joints; but there is the usual 

 slight overlapping, and all are strengthened on the inner side 

 by a vertical median rib. 



Specific determination. 

 In his original description of the genus Semionotus, Prof. 



