254 Annals of the South African Museum. 



half the size of the type specimen. It is probably an upper tooth. 

 It has apparently had five ridges, and may belong to a different- 

 species. It is most probably an immature tooth. 



Of described forms this Vaalbank specimen seems to come 

 nearest to C. serratus and C. Philiipsi of Agassiz. 



HELICHTHYS BKOWNI, g. et sp. n. 



This interesting little Palaeoniscid is represented by a considerable 

 number of specimens in Mr. Brown's collection, by one or two in 

 the collection sent to the South African Museum by Dr. Kannemeyeri, 

 and by one or two specimens in the collection of the Victoria College. 

 Many of the specimens are very well preserved, and almost every 

 detail of the external anatomy is revealed in one or other. For the 

 type I have taken one of Mr. Brown's specimens, which, though 

 without the tail, is the most perfect otherwise. 



General Form. Most of the specimens measure about 90 mm. in 

 length, and the body is about 18 mm. deep behind the pectoral fins. 

 The length of the head with the opercular apparatus is about 21 mm. 

 The dorsal and anal fins are well developed and triangular, the 

 dorsal being very slightly in advance of the anal. The tail is 

 typically Palaeoniscid. 



Head and Opercular Apparatus. The skull differs from that of 



the majority of Palasoniscid genera in having the suspensorium, 



as in Amblypterus, nearly vertical. The frontal bone is long and 



narrow, and each is traversed by a sensory canal which opens on 



the surface by a series of foramina. On the outer side of each 



frontal are, as in Nematoptycliius as figured by Traquair (6), a 



posterior frontal and an anterior frontal, to use Traquair's names ; 



and in front of the frontals doubtless a median ethmoid. It is not 



well preserved in any of the specimens, but in one the place for it is 



well shown between the anterior frontals. Immediately behind the 



frontals are a pair of small parietals. These are relatively smaller 



than in Palaoniscus and considerably smaller than in Nematoptycliins. 



The supratemporal region has hitherto been only known in a 



very few Palaeoniscids. In Palceoniscus Traquair says (6, p. 21) : 



" The presence of a narrow supratemporal chain of ossicles behind 



the posterior margin of the cranial buckler is probable, though not 



satisfactorily exhibited in any specimen I have had the opportunity 



of examining. I have, however, observed what seems to me to be 



decided traces of their presence in Palceoniscus, and ... I have 



indicated them in dotted lines [in the figure]." In Elonichthys 



pectinatus, however, he discovered a series of well-developed 



