2o6 



ANASPIDA 



Lasanius, Traq. ; Silurian, Scotland (Fig. 179). 



Family Euphaneropidak. Small scattered shagreen granules are 

 found on the head, enlarging on the trunk into narrow scales disposed 

 much as in Birkemia ; towards the tail are some quadrangular scales 

 with enamel-like surface. The granules extend on to the fins, in which 

 traces of dermal rays and also of endoskeletal supports can be made 

 out. The ventral row of scutes is less marked than in the other families 

 [503a]. 



Euphanerops, A. S. Woodward ; Upper Devonian, Canada. 



Order 4. PTERICHTHYOMORPHI (Antiarchi). 



This is a small compact group of Ostracodermi, remarkable for 

 the great development of the dermal armour. The plates and scales 

 are of true bone, with bone -cells throughout; their surface is or- 

 namented with tubercles and ridges, but bears no distinct evidence 

 of having been formed of fused denticles (Fig. ISO). Vascular 





Fig. ISO. 



Enlarged view of a small piece of the shield of Bothriolepis canadensis, Wlit. ; Upper 

 Devonian, Canada, i, inner bony lamellae ; l.v, large vascular space; m.l, middle vascular 

 layer ; o.l, outer bony lamellae ; s, surface ornament. 



cavities are developed in the middle layer, and the inner layer is 

 lamellated as usual. A very complete and accurate knowledge of 

 the outer structure of these Palaeozoic fish has been obtained of 

 late years from the researches of Pander [312], Traquair [452, 461], 

 A. S. Woodward [503, 505], Patten [328], and Eohon [370]. 



The broad rounded head is covered with a shield, which articu- 

 lates behind with a larger trunk shield or cuirass, completely 

 surrounding the body. Both are composed of closely united plates, 

 separated by fine sutures. The tail-region bears a dorsal fin and 

 an unforked heterocercal fin (Fig. 181). An anterior dorsal fin-fold 

 has been described in Bothriolepis immediately behind the carapace 



