Fossil Fishes of tJie Upper Karroo Beds of South Africa. 265 



type is a fairly well-preserved specimen there were a number of 

 points left in doubt which can now be settled. I have only seen 

 three specimens of this species and only one approaching perfection. 

 Though the head is fairly well preserved it is very difficult to make 

 out the sutures owing to the large numbers of ganoine tubercles 

 scattered over the bones. In the numerous specimens of the following 

 allied species the cranial details are somewhat better seen. 



The operculum and subopercular are well preserved in a number 

 of specimens, the latter being nearly twice the size of the former. 

 In front of these lies a large curved bone about half the width of the 

 operculum and extending from the level of the upper border of the 

 operculum to the middle of the subopercular. Smith- Woodward in 

 characterising the genus Clcithrolepis (B. M. Cat., vol. iii., p. 155) 

 states, " the preoperculum narrow and almost covered by the sub- 

 orbitals." I feel satisfied this is not the case in Cleithrolepis minor 

 at least, for in it clown the relatively broad preopercular runs the 

 sensory canal in almost exactly the same way as is seen in the 

 preopercular of Semionotus. The circumoculars are small bones 

 which form a ring round the orbit, the one at the upper and 

 posterior corner of the orbit being the largest. A canal seems to 

 run up over the head in the supratemporal region and another 

 branch down the frontal and round the front of the orbit. Above 

 the operculum there seems to be a fairly large squamosal traversed 

 by the anterior continuation of the lateral line. And there is some 

 evidence of a second canal running parallel to the other above it. 

 In one of the specimens of Cleithrolepis extoni the parasphenoid 

 is well seen. The maxilla and mandible are very short. If there is a 

 distinct interoperculum it is very small. Three or four branchiostegal 

 rays can be detected in one of the specimens of C. minor. 



The pectorals are not preserved in any of the specimens of 

 C. extoni I have seen though the place of 'attachment is manifest, 

 and only a trace of the pelvic fin is preserved. In all three speci- 

 mens the dorsal fin is nearly perfectly preserved. It consists of 

 20 rays with a series of small fulcra in front. The anal fin is 

 shorter than the dorsal and consists only of 15 rays. Both fins 

 extend to near the base of the tail. The caudal fin is large and 

 symmetrical, but not very deeply cleft, and the longest rays are only 

 a little longer than the longest of the dorsal and anal fins. There 

 are altogether 30 rays in the caudal fin and a series of small fulcra 

 both above and below, and all the rays are articulated and bifurcated 

 distally. 



The greatest length of the complete fish from the snout to the line 



