L. 31. Lambe — Fish fauna of the Albert Shales. 169 



Elonichthys browni (Jackson). 



Pakeo?iisciis brownii, Jackson 1851. Report on the Albert Coal 



Mine, etc., Boston, p. 22, plate I, figs. 2 and 5, plate II, fig. 



1, and plate I, ? fig. 4. 

 Palceoniscus brownii and P. jacksonii Dawson, 1811. Canadian 



Naturalist, new series, vol. 8, p. 339. 

 Palceoniscus (Elonichthys) brownii and P. jacksonii Dawson, 



1878. Acadian Geology, 3d edition, supplement, p. 101. 



A species of moderately large size, reaching a length of Z^l'S™ 

 (about 15 inches). Maximum depth of the trunk, slightly in 

 advance of the pelvic tins, contained about three and three 

 quarters times in the total length. Length of head, including 

 the opercular apparatus, about one-fifth of the total length. 

 Fins rather large. Pectoral fin powerful, spreading, with a 

 restricted base ; rays articulated except the first two or three 

 anterior ones proximally. Pelvic fins, small in comparison 

 with the other fins, about midway between the pectoral and 

 anal fins, in advance of the mid-length of the trunk. Anal fin 

 large, triangular, with a broad base, reaching posteriorly close 

 to the tail. Dorsal fin similar in shape to the anal but not 

 quite as large, the center of its base nearly above the anterior 

 end of the base of the anal. Caudal fin large, the body 

 prolongation of the upper lobe robust, extended, the lower 

 lobe well-developed. Fulcra in all the fins conspicuous. 

 External bones of the head ornamented with definite ridges 

 of varying length, straight or slightly tortuous and having a 

 general longitudinal direction, replaced at times by tubercles. 



Flank scales near the head (figure 3), sculptured by 

 from sixteen to twenty striations running obliquely backward 

 except in the anterior lower portion of the scale surface where 

 they are parallel to the lower margin. Posterior margin ser- 

 rated. Usually in passing backward on the trunk, the striae 

 decrease in number and gradually disappear, being replaced 

 by a few punctations, the surface of the scales becoming 

 smoother and the serrations fewer in number, figure 4, until 

 in the upper lobe of the tail both punctations and serrations 

 are lost, leaving the scales smooth. It is found, however, that 

 the striations of the scales persist in a variable degree, in differ- 

 ent specimens, in the posterior half of the trunk, and in 

 some even the caudal scales retain a number of the strise. 

 Between the dorsal and anal fins the flank scales are nearly 

 twice as long as high with a considerable overlap, but near 

 the head they have more the form of a rhombus. The 

 exposed surface of the anterior flank scales is higher than long. 



Enlarged, longitudinally striated, imbricating dorsal ridge 



Am. Jour. Sci.— Fourth Series, Vol. XXVIII, No. 164.— August, 1909. 

 12 



