22 PISCES class i 



Family 2. Diplacanthidae. Smith Woodward. 



Two dorsal fins. Free spines between paired fins conspicuous. Upper Silurian 

 to Upper Devonian. 



Diplacanthus, Ag. (Ehadinacanthus, Traquair). Trunk fusiform, probably 

 not much laterally compressed. Teeth minute or absent ; orbit with ring of 

 four circumorbital plates. Pectoral fins large, and a median pair of stout 

 spines fixed between these to the well-developed basal supports ; a single pair 

 of free spines between the pectoral and pelvic fins. D. striatus, Ag., about 

 0*1 m. in length, and other species from the Lower Old Eed Sandstone of 

 Scotland. D. horridus, Smith Woodward, from Upper Devonian, Scaumenac 

 Bay, Canada. 



Ischnacanthus, Powrie (Ictinocephalus, Page). Much resembling Diplacanthus. 

 but the inner pectoral spines wanting, and the jaws provided with a powerful 

 dentition. A few large, smooth, conical teeth alternating with minute cusps. 

 Scales smooth. /. gracilis, Egert. sp., from Lower Old Red Sandstone, Turin 

 Hill, Forfarshire. 



Climatius, Ag. {Brack //acanthus, Egert.), (Fig. 39). Trunk fusiform and 

 laterally compressed. Teeth minute or absent ; orbit with ring of four 

 circumorbital plates. Fin spines remarkably broad and marked with coarse 



longitudinal ridges, 

 sometimes with posterior 

 denticles. Pectoral fins 

 not much larger than 

 the pelvic pair ; three 

 or four pairs of free 

 spines, resembling the 

 fin spines, between the 

 FlG - 39 - paired fins. C. reticu- 



Climatius scutiger, Bgerton. Lower Old Red Sandstone ; Forfarshire. /„/,„ \ ~ „,,,] r( Q ^,Uno^ 



Nat. size (after Powrie). UUUS, J±g., dllU U. SCUUgei , 



Egert. (Fig. 39), are 

 known by nearly complete fishes from the Lower Old Red Sandstone of 

 Forfarshire. Similar spines occur in the Passage Beds (Downtonian) of Here- 

 fordshire, and in the Lower Devonian of Campbellton, New Brunswick. 



Euth acanthus, Powrie. Essentially identical with Climatius, but with 

 narrower straight spines. Lower Old Red Sandstone, Forfarshire. 



Parexus, Ag. Much resembling Climatius, but the anterior dorsal spine 

 enormously elongated and with large posterior denticles, P. incurvus, Ag., 

 and P. falcatus, Powrie, from Lower Old Red Sandstone, Forfarshire. 



Order 3. ICHTHYOTOMI. Cope. 1 



(Proselach ii, Doderlein.) 



Endoskeleton well calcified, but no membrane calcifications. Pterygoquadrate arcade 

 movably articulated with the cranium. A T o circumorbital plates. Neural and haemal 



Beyrich, A'., Monatsb. Berlin Akad. 1848, pp. 24-33.— Br ongniart, C, Bull. Soc. Industrie 

 Mm. (Saint Etienne), ser. 3, vol. IJ. livr. 4, 1888.— Cope, E. I)., Proc. Amer. Phil. Soc. 1S84, p. 

 0/2 - — Davis, J. H'., On the fossil Fish-remains of the Coal Measures in the British Islands. I. 

 Pleuracanthidae (Trans. Roy. Dublin Soc. ser. 2, vol. XII.), 1889.— Doderlein, L., Zool. Anzeig. vol. 



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