FISH OF THE OLD RED SANDSTONE. 



39 



very minutely and uniformly punctured as in Osteolepis and 

 Diplopterus. Total length about 7 inches, greatest width of 

 body 1^ inch, length of body scales 1 J line. 



So completely identical are the plates of the head of this fish 

 with those of the large imperfect example figured by Agassiz (Pois. 

 Foss. vol. ii. pi. 2 h, fig. 2), that I cannot help suspecting that 

 that figure may represent a portion of a fish of the present spe- 

 cies, the imperfection of the retral part of the body having per- 

 haps permitted M. Agassiz to refer it to the Osteolepis macrole- 

 pidotus, although even without seeing the fins we might distin- 

 guish it by its wide, rapidly tapering figure from that species, 

 which is correctly represented by the fig. 1 of the same plate so 

 far as it goes. The teeth are minute, slender, conical, rather 

 distant, apparently in several rows, and of irregularly unequal 

 size. I have examined three perfect specimens of this species 

 presented to the University collection at Cambridge by the Rev. 

 W. PoUexfen, by whom nearly all the Orkney fishes here noticed 

 were collected, and whose zeal I am happy to commemorate by 

 dedicating this to him. 



Not uncommon in the flags of the old red sandstone at Orkney. 



{Col. University of Cambridge.) 



(CCELACANTHI.) 



Gyroptychius (M'Coy), n. g. 



Gen. Char. Slender elongate ganoid fishes, with large semi-oval 

 depressed heads, from which the body gradually tapers to the 

 tail, which is diphycercal, the caudal fin being rhomboidal, 

 pointed in the middle of the retral margin, and the prolonga- 

 tion of the body extending a little above the medial line nearly 

 to the end ; two small elliptical dorsal fins exactly opposite two 

 similar anal fins ; pectoral fins broad, rounded, placed rather 



far back : scales subrhom- ^ , „ ^ , , . 



u -J 1 J.^ n ^ ^ J^cales ot Gwro«rwcA?M5 X two diameters. 



Doidal on the flanks, nearly y t- j 



oval on the back, imbri- 

 cated, the exposed portion 

 of each with minute rough 

 ridges which converge to- 

 wards the retral end, seem- 

 ing to gyrate round a nearly 

 central point ; the anterior 

 concealed portion nearly 

 smooth (or under a strong 

 lens minutely radiated as 

 in Holoptychim) ; under surface of each scale nearly smooth, 

 with a strong mesial keel which extends from the anteal edge 



a. Dorsal 'scale : up- 

 per surface. 

 h. Do. under surface, 

 c. Lateral scales. 



