46 



PISCES 



CLASS I 



Family 3. Myriacanthidae. Smitli Woodward. 



Trunk elongated. Two upper pairs and one lower pair of thin Jental plates, 

 also a stouf, median, incisor-like tooth at the Symphysis of the inandible. Head with 

 a few dermal plates. Males with a prehensile spine on the snout. Anterior dorsal 

 fin above the pedorals, with a long, straight, robust spine. Jurassic. 



Myriacanthus, Ag. (Prognathodus, Egerton ; Metopacanthus, Zittel). Rostrum 

 with a terminal cutaneous flap. Anterior upper dental plate smaller than the 

 posterior plate. Dorsal fin spine long and slender, somewhat laterally com- 

 pressed, with a large internal cavity ; sides ornamented with small tubercles ; 

 a series of large, thorn-shaped tubercles arranged along each edge of the 

 fiattened posterior face, passing into a single median row distally, and a single 

 series of similar denticles on the anterior border. Kostral spine elongated 

 'and pointed, with expanded base. Dermal plates tuberculated. M. paradoxus, 

 Ag., and M. granulatus, Ag., from Lower Lias of Lyme Regis. 



Chimaeropsis, Zittel (Fig. 91). Mandibular dental plates (md), slightly 

 arched, with a large tritoral area ; the symphysial tooth (x) externally 



Fig. 91. 



Chimaeropsis paradom, Zitt. Upper Jurassic (Litliographic Stoue) ; Bichstädt, Bavaria, 1/2 iiat. size. 

 md, Mandibular tooth ; p, Minder upper tooth; v, Anterior upper tooth in side view; v^, 8anie from lower 

 side ; x, Slender premandibular tooth. 



(inferiorly) convex, internally (superiorly) fiat or concave. Anterior (v) and 

 posterior (p) upper dental plates triangulär, the former not smaller than the 

 latter, and tapering in front, the latter tapering behind. Fin spine as in 

 Myriacanthus. Body covered with small, conical, radiately grooved placoid 

 scales. Upper Jurassic (Lithographie Stone) of Bavaria. 



Family 4. Chiraaeridae. Chimaeras.i 



Trunk elongated, shark-like. Teeth forming two pairs of robust dental plates in 

 the upper jaw, the foremost the smaller, both pairs thickened and closely apposed in 

 the longitiulinal mesial line of the mouth •; lower dentition comprising a single pair of 

 beak-shaped plates meeting at the Symphysis ; the plates usually with several tritors. 

 Pedoral fins very large, fan-like, with simple, horny rays ; anterior dorsal fin above 

 the pedorals, ivith a large spine articulated to a cartilaginous base ; posterior dorsal 



1 Xewton, E. T., Tlie Chiniaeroid Fislies of the Britisli Cretaceous Rocks (Meni. Geol, Survey, 

 Mon. No. IV.), 1878. 



