Several other genera belong to the family Carchariidæ, but it will be sufficient to mention their names:--_Hemigaleus_, _Loxodon_, _Thalassorhinus_, _Triænodon_, _Leptocarcharias_, and _Triacis_. SECOND FAMILY--LAMNIDÆ. _Eye without nictitating membrane. Anal fin present. Two dorsal fins; the first opposite to the space between pectoral and ventral fins, without spine in front. Nostrils not confluent with the mouth which is inferior. Spiracles absent or minute._ All the fishes of this family attain to a very large size, and are pelagic. But little is known of their reproduction. The first appearance of this family is indicated by _Carcharopsis_, a genus from carboniferous formations, the teeth of which differ from those of _Carcharodon_ only by having a broad fold at the base. In the chalk and tertiary formations almost all the existing genera are represented; and, besides, _Oxytes_, _Sphenodus_, _Gomphodus_, and _Ancistrodon_, which are known from teeth only, have been considered generically distinct from the living Porbeagles. LAMNA (OXYRHINA).--The second dorsal and anal are very small. A pit at the root of the caudal, which has the lower lobe much developed. Side of the tail with a prominent longitudinal keel. Mouth wide. Teeth large, lanceolate, not serrated, sometimes with additional basal cusps. On each side of the upper jaw, at some distance from the symphysis, there is one or two teeth conspicuously smaller than the others. Gill-openings very wide. Spiracles minute. [Illustration: Fig. 113.--Upper and lower tooth of Lamna.] Of the “Porbeagles,” three species have been described, of which the one occurring in the North Atlantic, and frequently straying to the British coasts (_L. cornubica_), is best known. It attains to a length of ten feet, and feeds chiefly on fishes; its lanceolate teeth are not adapted for cutting, but rather for seizing and holding its prey, which it appears to swallow whole. According to Pennant it is viviparous; only two embryoes were found in the female which came under his observation. Haast has found this species also off the coast of New Zealand. CARCHARODON.--The second dorsal and anal are very small. Pit at the root of the caudal, which has the lower lobe well developed. Side of the tail with a prominent longitudinal keel. Mouth wide. Teeth large, flat, erect, regularly triangular, serrated. On each side of the upper jaw, at some distance from the symphysis, there is one or two teeth conspicuously smaller than the others. Gill-openings wide.