PISCES 



CLASS I 



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Fig. 51. 



S. hybodoideSf Egert. sp., represented by fin spines and teeth in English, 



Welsh, and Scottish Goal Measures. 



Hybodus, Ag. (Meristodon, Ag.), (Fig. 51). Teeth and dorsal fin spines 



almost as in Sphenacanthus ; but double series of denticles on hinder face of 



fin-spine median, not laterally placed. 

 Symphysial teeth few and relatively 

 large. Notochord persistent, but ver- 

 tebral arches calcified. One or two 

 large hook-shaped, semi-barbed dermal 

 spines (Sphenonchus) immediately behind 

 each orbit, at least in the male. Shagreen 

 sparse, consisting of small conical, 

 radiately grooved tubercles, which are 

 sometimes fused into groups of three. 



Numerous species ranging from the Trias to the Lower Cretaceous. Teeth 



of H. plicatiUs, Ag. (Fig. 51, A), abundant in the Muschelkalk. Nearly 



complete skeletons from the Lower Lias of England (H. delabechei, Charles- 



worth ; H. reticulatus, Ag., Fig. 51, ^) and the Upper Lias of Würtemberg (H. 



hauffianuSj Eb. Fraas). Fine skulls from Wealden, Pevensey Bay, Sussex 



{R. basanuSf Egert.). 



Acrodus, Ag. (Thedodus, Plieninger), (Fig. 52). A genus only differing 



from Hybodus in the rounded, non-cuspidate character of the teeth. Common 



Teeth ofif//öodws. A, H. plicatiUs, Ag. Muschel- 

 kalk ; Laineck, iiear Bayreuth. B, H. reticulatus, 

 Ag. Lower Lias ; Lyme Regis, Dorsetshire. C, H. 

 polyprion, Ag. Lower Oolite (Dogger) ; Stonesfield, 

 Oxfordshire. 



Fio. 52. 



Acrodus anningiae, Ag. Dentition, 1/3 natural size. Lower Lias ; Lyme Regi 

 A, Symphysis. B, Detached tooth, seen from side and above, natural size. 



in the Triassic and Jurassic, and ranging to the Upper Cretaceous. A. 

 gaillardoti, Ag., teeth from Bunter, Muschelkalk, and Keuper of Germany 

 and France. A. minimus, Ag., common in European Keuper and Rhaetic. 

 A. anningiae, Ag. (Fig. 52), and A. nobilis, Ag., known by fine specimens from 

 the Lower Lias, Lyme Regis. A. levis, Sm. Woodw., teeth from English 

 Gault. 



Palaeobates, Meyer. Teeth depressed, rounded, without lateral denticles 

 and not keeled. European Triassic. 



Asteracanthus, Ag. (Strophodus, Ag.; Curtodus, Sauvage), (Figs. 53, 54). 

 Principal teeth elongated, irregularly quadrate, with slightly arched but 

 flattened crown ; symphysial teeth few, smaller but relatively large, much 



