54 



FISH GALLERY. 



and internally to these projections are movable flaps of elliptical 

 shape above the gill-chambers. The scales on the side of the 

 trunk region are high and narrow. Remains of Cephalaspis 

 occur in the Lower Old Red Sandstone of Scotland and the 

 Devonian of Canada. 



Pterickthys (fig. 31) is represented by a model of Pterichthys 

 milleri (165) enlarged four diameters. In Pterichthys the head- 

 plates are so grouped and so separated from the body-plates as to 



Fig. 31.— Restoration of Pterichthys testudinarius. 

 A, upper view ; B, lower view. 



suggest that the head was movable upon the body. The lateral 

 line grooves are well marked ; the eyes are close together. A pair 

 of limbs articulate at the front of the body region and consist of a 

 hollow skeleton of dermal plates, presumably filled in life by 

 muscles, &c. There is a median dorsal fin ; the tail is heterocercal 

 and its sides are covered with imbricated scales. Remains ^of 

 Pterichthys occur in the Lower Old Red Sandstone of Scotland 

 and in the Devonian of the Eifel district. Visitors may be 

 interested to know that a cardboard model of Pterichthys 

 constructed by Hugh Miller is on exhibition in the Gallery of 

 Fossil Fishes in the Geological Department of the Museum. 



