DEPOSITS OF ORANGE FREE SIATE, SOUTH AFRICA. 141 



II. Cleithrolepjs Extoni, sp. nov. (PI. YT. figs. 6 & 7.) 



The latest specimens received from Dr. Extori arc two imperfect 

 examples of a deep -bodied Ganoid fish from llouxville, Orange Free 

 State. The larger specimen (fig. G) is destitute of most of the head 

 and caudal fin, while the smaller exhibits only a portion of the 

 trunk, with the operculum aiid postorbital bones, and the pectoral fin. 



The general proportions of the fish are well shown in the figure 

 just quoted. The head is relatively small; pelvic fins are present ; 

 the anal and dorsal fins are similar and opposite ; and the u])per 

 lobe of the caudal pedicle is atrophied. 



Head and Opercular Fold. — ^An undeterminable fragment of the 

 roof- bones is the only portion of the cranium exposed to view, and 

 the more superficial circuraorbital elements are in such a state of 

 preservation that the sutures can only be indistinctly recognized 

 (fig. 7). There is also some appearance of a chain of three small 

 membrane bones extending backwards from the postero-superior 

 angle of the circumorbitals, above the operculum, and between it 

 and the cranial roof, and these, as in Polypterus and some other 

 Ganoids, are perforated by the " lateral line " as it passes upon the 

 head. The fossil (fig. 7) shows the sensory canals very clearly ; 

 from the second of the three ossicles, one branch is directed upwards 

 across the occiput, while further forwards the line divaricates, one 

 division passing over the orbit and the other downwards. There 

 are also other portions of the " lateral line " system beyond the 

 occipital region, the precise connexions of which are not shown. 



No preoperculum or interoperculum is recognizable, but the oper- 

 culum and suboperculum are shown in both the specimens. The 

 operculum (op) is almost square, with the postero-superior angle 

 rounded off, and it is considerably smaller than the suboperculum 

 (,s\op), having only about two thirds the vertical extent of the 

 latter. In the large fossil (fig. 6) there are likewise faint impres- 

 sions of two or three short and broad branchiostegal rays beneath 

 the suboperculum ; and all these bones, as well as those of the head, 

 exhibit a superficial ornament of sparsely scattered ganoine tubercles. 



Appendicular ^Skeleton. — Of the paired fins the pectorals are 

 placed laterally, being situated in a position almost on the level of 

 the lower border of the suboperculum. So far as can be ascertained 

 from the smaller fossil (fig. 7), each fin seems to have consisted of 

 about 10 delicate rays, ornamented externally with tubercles, but 

 the state of preservation is too imperfect to allow of determining any 

 more precise structural features. The pelvic fins are even more 

 indistinctly shown, though the large specimen (fig. 6) indicates that 

 these were very small, and placed almost midway between the head 

 and the commencement of the anal. 



Of the median fins, both the dorsal and anal are nearly complete. 

 The former consists of about 18 stout rays, each articulated, at mo- 

 derate distances, beyond a point near the base, and dividing dis- 

 tally ; and in front of the fin there are some indistinct small fulcra. 



{loc. cit.) as consisting of "a belt of ribbon sandstone, some parts of whicb, 

 when worked down, show a beautiful ribbon-pattern of varying colours — red, 

 white, yellow, and light buff." 



