162 PALEONTOLOGY. 



Elonichthys, from the coal of Wettin, with longitudinally 

 striate jaw-bones, and radiately striate skull-bones, combines 

 certain characters of the two above-named genera. 



Plectrolepis, from the coal of Scotland, with thick 

 and densely enamelled scales, having four or five spines 

 on their hind border, is also characterized by a more ad- 

 vanced position of the dorsal fin than any other genus of 

 Palceoniscidce. 



Family VI. — Saurichthyid^e. 



Magnificent species of heterocercal rhomb-scaled Ganoids, 

 with large dispersed laniary teeth, sometimes of a size rivalling 

 those of great Saurians, for which they have been mistaken, 

 have left their remains in the coal strata at Carluke, near 

 Glasgow, and other localities, and constitute the genus Mega- 

 lichthys of Agassiz. The head is defended by strong ganoid 

 plates, of a beautiful polish ; the trunk-scales are usually 

 granulate exteriorly. In this genus, as in the type of the 

 family, the fulcra of the fin-rays are in two rows. The type- 

 genus Saurichtliys has the teeth lodged in an alveolar groove, 

 as in the Ichthyosaur, the crown being divided by a slight 

 constriction from the base : all the known species of Sau- 

 richtliys are triassic. S. longidens is from the bone-bed at 

 Aust. Cliff, Bristol. 



Family VII. — CATURimE. 



Homocercal rhombo-ganoids, with a short dorsal fin, and 



some of the teeth much larger than the rest, and 



laniariform. 



Genus Caturus. — In this genus the jaws are armed with 



close-set, large, conical teeth ; the scales are delicate ; the fins 



are of moderate size ; all the species are homocercal and 



