PEDIGREES. 177 



distinct parts, a lobe-shaped central and basal 

 portion, surrounded by a marginal or fringed 

 portion. The former is constituted by the 

 muscles covering the axial portion of the 

 skeleton, and the latter by delicate fin-rays 

 connected with the central or axial portion. 



Of the fringe-finned fishes, as Dr Smith 

 Woodward points out, there are two distinct 

 types, distinguishable by the form of the pectoral 

 fins (fore-limbs). In all the extinct members 

 these fins are attached to what corresponds with 

 the shoulder girdles of the higher vertebrate by 

 a single support, whilst in the other type these 

 fins are attached to the girdle by means of three 

 separate elements placed side by side. A refer- 

 ence to the accompanying figures (fig. 7, p. 66), 

 should make this clear. The latter type of fin is 

 called a tribasal, the former a unibasal fin. The 

 tribasal fin is found only in living forms. 



In some respects these fringe-finned fishes 

 resemble the lung-fishes, but whether this re- 

 semblance is due to adaptation to similar physical 

 conditions or to actual affinity, is a matter for 

 debate. The evolution of the group is accom- 

 panied by specialisation in many directions, 

 details of which will be found in more profound 

 works. 



The remains of these fishes, which we dig up 

 to-day as fossils, are but samples of the denizens 

 of the ancient lakes and inland seas, whose dried 

 basins form the rocks known as the old red 

 sandstone. The most characteristic feature of 

 these remains is the nature of the form of the 

 scales. These, in the majority of the fossils 



M 



