No. 6.] DAWSON — CARBONIFEROUS FISHES. 339 



teriorly. The posterior edge of the anal fin approaches nearly 

 to the caudal, and extends considerably behind the posterior 

 edge of the dorsal. 



P. Cairnsii, Jackson. — About the same size with the last, but 

 more slender, and the head less obtuse in front. Scales think 

 and with few striae, and less numerous serrations. Dorsal scales 

 pointed posteriorly. Anal fin somewhat remote from caudal and 

 opposite dorsal. 



A specimen collected by Mr. Ells, of the Geological Survey, 

 indicates a fish of the same general form with P. Alberti, but 

 about six inches long. The outline of this fish is well seen, but 

 the details are not sufficiently clear to show if it differs in these 

 from the smaller species. 



The next species and perhaps the following one, belong to 

 the genus Eloniehthys of Giebel. They are much larger than the 

 preceding. 



P. Brownii, Jackson, is deep in form, with large dorsal and 

 anal, the latter reaching almost to base of caudal. Scales of body 

 broad and with numerous fine horizontal striato-punctate fur- 

 rows, which turn abruptly upward at the anterior side of each 

 scale. A nearly perfect specimen, collected by Mr. Ells, shows 

 that the head was of moderate size, and the body about ten 

 inches long and three and a quarter inches wide, the breadth at 

 the dorsal fin being as great as at the shoulders, giving a sort of 

 rectangular form to the fish, whose breadth suddenly diminishes 

 toward the tail. 



The crystalline lens of "the eye of Mr. Ells's specimen is pre- 

 served in calcite. Under the microscope it shows concentric 

 laminse and coarse bands or rods with indistinct denticulations; 

 the structure being similar to that in the crystalline lens of the 

 modern ganoid Amia ocellicauda. This is the first instance 

 known to me of the preservation of the structure of the crystal- 

 line lens in a palaeozoic fish. 



P. Jacksoni, n. s. — A species figured, but not ^described, by 

 Jackson, is represented by many fragments in my collection. It 

 is the largest of these fishes, reaching a length of 15 inches. 

 It may be distinguished from the last by its more slender form, 

 its small anal fin, more remote from the caudal, and by the char- 

 acter of the scales, which have many horizontal striae, and have 

 in the broader ones a few deep and strong serrations posteriorly. 



