22 



PISCES 



Family 2. Diplacanthidae. Smith Woodward. 



Two dorsal fins. Free spines between jKcired fins conspicvous. Upper Silurian 

 to Upper Devonian. 



Diplacantlms, Ag. (FJiadinacantJms, 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 

 O'l m. in length, and other species from the Lower Old Red Sandstone of 

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

 Bay, Canada. 



Ischnacanthus, Powrie {Idinoceplicdns, Page). Much resembling Diplacantlms, 

 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. J. gracilis, Egert. sp., from Lower Old Red Sandstone, Turin 

 Hill, Forfarshire. 



Climatius, Ag. (Brachyacantkus, Egert.), (Fig. 39). Trunk fusiform and 

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

 Fin spines remarkabl}'^ broad and marked with coarse 



longitudinal ridges, 

 sometimes with posterior 

 denticles. Pectoral fins 

 not much lai-ger than 

 the pelvic pair ; three 

 or four pairs of free 

 spines, resembling the 

 fin spines, between the 

 paired fins. C. reticu- 

 latus, Ag., and C. scutiger, 

 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. 



Eutliucanthus, Powrie. Essentially identical Avith Climatius, but with 

 narrower straight sjoines. Lower Old Red Sandstone, Forfarshire. 



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

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

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



circumorbital plates. 



Fig. 39. 



Cliinat ins scut igrr, Egerton. Lower Old Red Sandstone; Forfarshire. 

 Nat. size (after PowTie). 



Order 3. ICHTHYOTOMI. Cope.i 



(Proselachii, Doderlein.) 



Endoskeleion well calcified, but no membrane calcifications. Pterygoquadrate arcade 

 movabhj articulated icith the cranium. No circumorbital plates. Neural and haemal 



' Beyrich, K, Monatsh. Berlin Akad. 1S48, pp. 2A-ZZ.—Brmgniart, C, Bull. See. Industrie 

 Miu. (Saint Etienue), ser. 3, vol. II. livr. 4, 1888.— C'o/^e, E. iJ., Proc. Amer. Phil. Sec. 1884, p. 

 572. — Davis, J. H'., Ou 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. 



