100 



PISCES. 



species. In some forms the marginal teeth are simply pointed, in others 

 they exhibit slightly bilobate crowns. The typical species, D. politus 

 (fig. 70), from the Lower Lias of Lyme Regis, has smooth scales and 

 attains a length of about 0'4 m. The largest known species, D. granu- 

 lattis, from the same formation and locality, has tuberculated or pustulate 

 scales, and is sometimes O6 m. in length. 



Aetheolepis (fig. 71). A deep-bodied fish much resembling Dapedius 

 and having nearly similar rhombic scales in the abdominal region, while 

 these gradually pass into thin, deeply-overlapping, cycloidal scales in the 

 caudal region (fig. 71). All the scales are ornamented with tubercles of 

 ganoine. The only known species is A. mirabilis from the Jurassic of 

 Talbralgar, New South Wales. 



FIG. 71. 



Aetheolepis mirabilis ; series of scales of one individual, nat. size, showing 

 gradual passage from anterior articulated rhombic scales to posterior over- 

 lapping cycloidal scales. Jurassic ; New South Wales. 



Cleithrolepis. Another deep-bodied fish of irregular form, with 

 conspicuous ridge-scales and all the flank-scales very deep, exhibiting a 

 thick inner rib and large peg-and-socket articulation. The dorsal and 

 anal fins are opposite and not much extended. It occurs in the sup- 

 posed Triassic of New South Wales (C. granulatus from the Hawkesbury 

 Beds) and South Africa (C. extoni from the Stormberg Beds of Orange 

 Free State). 



The family of Macrosemiidae is closely related to that of the 

 Seniionotidae, but comprises small-mouthed fishes with elongated 

 trunk and extended dorsal fin. They range throughout the 

 Mesozoic Period. The least specialized genus, Ophiopsis, seems 

 to connect it with the family of Eugnathidse described below 

 (p. 106). The dorsal fin is usually single, though sometimes 

 (e.g., Notagogus arid Propterus) subdivided into two parts, and 



