Table-case, 

 No. C. 



84 P roselachii — IcMhyotomi. 



bones, and shagreen granules : tlie teeth probably bear another 

 name. AcondylaranfJms resembles the spiue of a Ray ; and 

 Erisinacarithns and LispacautJms are very suggestive of the 

 rostral spine of male Chimjeroids. 



These ichthyodorulites show that the earliest Elasmo- 

 bi-anchs differed very much from the existing members of the 

 sub-class. The fact is further emphasised by the discovery of 

 several Elasmobranch skeletons of Devonian, Cai-boniferous, 

 and Permian age, v^d^ch show that at least three extinct orders 

 are represented. 



OuDER I. — Proselachii. 



The first of these orders is that of the Prosklachii,, 

 represented only by Oladoselache, from the Upper Devonian 

 of Ohio, U.S.A. This is a notochordal shark without spines or 

 armour, except a ring of plates round the eye ; its paired fins 

 are mere balancers supported by parallel rods of cartilage, and 

 the teeth are identical with the detached Palaeozoic teeth 

 provisionally named Cladodus. Only fragments are exhibited. 



Wall-case, 

 No. 3. 



Table-case, 

 No. C. 



Okdei; II. — Ichthyotomi. 



The second ordei-, that of the IcHTHYOTOaii, is known by 

 numerous tolerably complete skeletons from the Carboniferous 

 and Lower Permian. Fine examples of the typical genus 

 Flenracaidhuft (Fig. 112) are exhibited from the Lower Permian 

 of Rhenish Prussia, Silesia, and Bohemia. The isolated spiues 

 of Plenracanthtis and the teeth known as Diplodus from the 



l''iG. ]r2. — f'l aroconthi'.x Ga.uUriii, Brougn. (roiuiatiou by C Brongui.irt) ; Coal-measures.. 

 Conimentiy, France. 



British Carbonifei-ous, especially Coal-measures, are also })laced 

 here. Like the Proselachii, these sharks are notochordal ; but 

 they differ in having jjaddle-shaped paired fins, supported by a 

 more or less branching arrangement of cartilages. The median 

 fins are very extensive, and there is usually a median dorsal 

 spine fixed at the back of the head. There is reason to believe 



