PISCES. 
71 
of Mount Lebanon in Wall-case 3, this genus being almost Wall-case 
identical with Mitsukurina now living off Japan. Numerous Tabl ^* cases 
isolated teeth and groups of teeth of the same family from 0"7 
Cretaceous and Tertiary formations are exhibited in Table- 
Fig. 70.—Jaw of Asteracanthus (Strophodus viedius) from the Great Oolite 
of Caen, Normandy; one-third nat. size. (Table-case 5.) 
cases 6 , 7, but it is impossible to name them satisfactorily, 
owing to the variation of shape always occurring in one and 
the same mouth. The existing genera Lamna , Oxyrhina , 
Odontasjois (Fig. 71), and Car char odon (Fig. 72), are repre- 
Fig. 71.—Tooth of Odontasjpis elegans, outer view, from the London Clay 
of Sheppey; nat. size. (Table-case 6.) 
sented. The teeth of the largest extinct species, Carcharodon 
megalodon, have an almost world-wide distribution in 
Miocene and Pliocene formations; and some examples have 
been dredged in a semi-fossil state, impregnated with the 
oxides of iron and manganese, from great depths in the 
existing oceans (see the “ Challenger ” dredgings in a middle 
