hi. PRESIDENT'S ADDRESS. 



As to their distribution in space, they have been found in the 

 West of England, in the East of Scotland, in Russia, in Gallicia, 

 and in the Eifel. The two pectoral-fins of Cephalaspis differ 

 from those of other Fish ; it is probable they had other functions 

 than those of mere locomotion, and were used to cause a current 

 of water to pass to the branchial organs, which were enclosed by 

 the great head-shield. 



Pterichthys, discovered by Hugh Miller in 1831. The body 

 carapace consists of osseous-plates united together, and closed 

 both above and below, and at the sides, but open in front for 

 the head, and at its distal end, for the tail. The head is repre- 

 sented almost entirely by a dorsal shield, formed of plates united 

 by sutures. The pectoral-fins, one on each side, are long and 

 slender ; they probably served to aid the fish to shuffle along the 

 sandy bottom, and if left dry at low-water enabled it to escape. 

 They remind one of a mammalian humerus. The head-shield is 

 semi-elliptic in shape, rounded in front and truncated behind, 

 where it meets the body carapace. The hinder extremity of the 

 fish terminates with a heterocercal caudal fin, covered with 

 osseous-plates. There are four genera, all of which belong 

 to the Old Red Sandstone period, differing from each other by 

 the overlapping of the anterior median dorsal plates. Many 

 acquainted with popular geology and palaeontology may be sur- 

 prised to find that the Asterolepis is not the Asterolepis of 

 Stromness, which obtained some notoriety through the writings 

 of Hugh Miller, which is a huge Coccostean. The name could 

 no longer be applied to Hugh Miller's Stromness fish, which is 

 now named Homosteus Millcri, Pander. Asterolepis now stands 

 as a genus independent of Plcrichthys, and is represented in this 

 country by Asterolepis maxima, of Agassiz, from the Upper Old 

 Red Sandstone of Nairn. 



Placodermi. This Sub-Order comprises the oldest vertebrate 

 remains, ranging from the Old Red Sandstone to the Carboni- 

 ferous Beds Pttrichthys. Head and trunk broad, the scutes 

 ornamented with tubercles, tail covered with scales slightly 

 imbricated. The cxo-skeleton is now well known, especially 



