LEPIDOGANOIDEI 129 



armed head, and arrested, as they passed, the minute airimals 

 on which it preyed. The animal world is full of such com- 

 pensatory defences ; there is a half-suit of armour given to 

 shield half the body, and a wise instinct to protect the rest. 

 Now it seems not improbable that the half-armed Coccosteus, 

 a heavy fish, indifferently furnished with fins, may have 

 burrowed, like the recent Sihirus Glanis or Pimelodus gulio, 

 in a thick mud, of the existence of which in vast quantity, 

 during the times of the old red sandstone, the dark Caithness 

 flagstones, the foetid breccia of Strathpeffer, and the gray 

 stratified clays of Cromarty, Moray, and Banff unequivocally 

 testify ; and that it may have thus not only succeeded in 

 capturing many of its light-winged contemporaries, which it 

 would have vainly pursued in open sea, but may have been 

 enabled also to present to its enemies, when assailed in its 

 turn, only its armed portions, and to protect its unarmed 

 parts in its burrow." * 



Sub- Order 2.— LEPIDOGANOIDEI. 

 Family I. — Dipterid^e. 



This family includes a few heterocercal fishes with a double 

 anal as well as dorsal fin. The head is large and flattened ; 

 the teeth subequal ; the scales perforated by small foramina ; 

 the notochord persistent. 



d'> 



a 2 



a/ v 



Fig. 47. 



Dipterus macrolepidotus (Devonian). 



In the genus Dipterus (fig. 47), the two dorsals, d 1, d 2, 

 are opposite the two anals, a 1, a 2 : the ventrals, v, are in 



* Hugh Miller, Rambles of a Geologist, p. 288. 

 K 



