Eastman: Triassic Fishes. 147 



as displaying the facial and opercular plates to better advantage than 

 in most specimens. 



On an Australian Genus of Semionotid/E (Pristisomus). 

 Much interest attaches to the Triassic fish-fauna of the Australian 

 region, on account of the peculiar structural features exhibited by 

 certain genera, the fact of its being to a large extent a "relict fauna," 

 and also on account of the knowledge it affords of the distribution of 

 well-known North American and European genera. All told not over 

 a dozen genera are known from the locality at Gosford, and their state 

 of preservation is not always of the best. It has seemed desirable to 

 illustrate one nearly complete example which has been placed in the 

 writer's hands for study by Mr. M. E. Crane of Pittsburgh, with 

 the understanding that it will eventually become the property of the 

 Carnegie Museum. 



Genus Pristisomus A. S. Woodward. 



This genus was established by Dr. A. S. Woodward in 1890 upon 

 the evidence of a number of fairly well preserved skeletons, which 

 exhibited characters intermediate between Semionolus and the geologic- 

 ally later and more highly specialized genus Dapedius. For example, 

 as pointed out in the original description of Pristisomus, "the long, 

 styliform teeth, and certain obscurely recognizable features in the 

 head, are most suggestive of Dapedius; and the depth of the trunk 

 nearly approaches that of some ot the species of the last-named genus. 

 The dorsal ridge-scales, however, and the proportions of the median 

 fins, more nearly resemble corresponding features in Semionotus, 

 though this well-known genus is distinguished by its dentition, the 

 absence of ventral ridge-scales, the slight vertical elongation of the 

 flank-scales, and the greater development and more forward position 

 of the dorsal fin." 



The typical species of Pristisomus is gracilis Woodward, from the 

 Lower Hawkesbury-Wiametta series (Upper Trias) of Gosford, New 

 South Wales. It is accompanied in the same formation by two other 

 species, P. latus Woodward and P. crassus Woodward, these three 

 being all that have thus far been described, and comparatively few 

 individuals are known of each of them. 



The general characters of Pristisomus are given by the original 

 author as follows: 



