﻿TSCHNAC ANTHTD-S!. 21 



This genus was withdrawn by J. Powrie in 1870 l , the type 

 species being assigned to Diplacanthus ; but it has lately been once 

 more adopted by R. H. Traquair 2 . 



Ischnacanthus gracilis (Egerton). 

 [Plate I. fig. 8.] 



1859. Ictinocephalus granulatus, D. Page, Rep. Brit. Assoc. 1858, Trans. 



Sect. p. 105 (name only). 

 1861. Diplacanthus gracilis, Sir P. Egerton, Figs. & Descrips. Brit. 



Organic Remains (Mem. Geol. Surv.), dec. x. p. 69, pi. ix. 

 1864. Ischnacanthus gracilis, J. Powrie, Quart. Journ. Geol. Soc. vol. 



xx. p. 419. 

 1870. Diplacanthus gracilis, J. Powrie, Trans. Edinb. Geol. Soc. vol. i. 



p. 290, pi. x. fig. 2. 

 1888. Ischnacanthus gracilis, R. H. Traquair, Geol. Mag. [3] vol. v. 



p. 512. 



Type. Nearly complete fish. 



The type species, attaining a maximum length of about 0-12-0-16. 

 Body slender and elongated, the greatest depth being contained 

 about five times in the total length. Fin-spines slender, coarsely 

 striated longitudinally. Pectoral fin-spines gently arched ; no pair 

 of free spines between these and the pelvic fins ; pelvic fin-spines 

 about two thirds as large as the pectoral, and placed midway 

 between these and the anal. Dorsal spines nearly equal in size, or 

 the second slightly the larger ; first dorsal spine placed well behind 

 the pectorals, second dorsal immediately behind the anal, which is 

 somewhat smaller. Scales smooth. Large dental crowns robust and 

 smooth. 



Form. Sf Log. Lower Old Red Sandstone : Forfarshire. 



All the following specimens were obtained from Turin Hill, near 

 Forfar :— 



38517. Small example. Purchased, 1864. 



38598-99. Nearly complete fish, displaying dentition ; and an im- 

 perfect large specimen, probably exceeding 0*16 in length. 

 Presented by James Powrie, Esq., 1864. 



41363-64. Trunk with complete tail, and an imperfect crushed 

 specimen. Purchased, 1869. 



46303. Imperfect trunk and tail, in counterpart, of an individual 

 probably 0*16 in total length. Purchased, 1875. 



1 Trans. Edinb. Geol. Soc. vol. i. (1870) p. 289. 



2 Geol. Mag. [3] vol. v. (1888) p. 512. 



