944 



CLASS PISCES. 



the Lebanon and in the Continental Miocene ; while allied extinct 

 genera are Pristiurus, from the Lower Kimeridgian of Bavaria, and 

 Mesitia, from the Lebanon beds. Finally, the existing Chiloscyl- 

 lium occurs in the Miocene of Wiirtemberg ; while Gingly mo stoma, 

 of which some of the existing species attain a length of 1 2 feet, is 

 represented in the Eocene of Alabama. 



Family Lamnid^e. — This family comprises the largest of the 

 Sharks, and is characterised by having the first dorsal fin placed 

 above the interval between the pectoral and pelvic fins, and 



without a spine. The teeth are acu- 

 minate, and when fully adult are 

 solid throughout. The earliest form 

 which has been referred to this family 

 is Carcharopsis, known by detached 

 teeth from the Carboniferous of Europe 

 and North America. The type genus 

 Lamna, in which Otodus may be in- 

 cluded, comprises the existing Por- 

 beagles, and has large lanceolate teeth 

 (fig. 870) with basal cusps, but without 

 marginal serrations. Teeth agreeing 

 with those of existing forms in their 

 general contour are found in Europe 

 from the Lower Miocene (fig. 870) 

 upwards, the so-called L. acuminata, 

 from the Chalk, belonging, however, 

 to the next genus. In another group of this genus, formerly known 

 as Otodus, the teeth (fig. 871) are distinguished by the great corn- 



Fig. 870. — Tooth of Lamna cus- 

 ftidata, from the Lower Miocene 

 (Oligocene) of Germany. (After 

 Zittel.) 



Fig. 871. — Tooth of Lamna appcndiculata, 

 from the English Chalk. 



Fig. 872. — Tooth of Oxyrhina plicatilis, 

 from the Hungarian Miocene. 



pression of the crown, the large basal cusps, and the shortness of 

 the root. Teeth of this type occur in Europe from the Gault to 

 the London Clay, and are also represented in the Upper Cretaceous 

 of Southern India and New Zealand. The nearly allied but extinct 

 genus Oxyrhina is characterised by the still greater compression of 



