THE ANTIARCHA. 377 



Habitat. Mode of Life. 



Mode of Preservation. — Nodules containing the heads, or other fragments of 

 Bothriolepis may be found on the beach, at the foot of the gray chifs in Miguasha, 

 near Dalhousie, New Brunswick; but the best specimens, showing the whole body, 

 can only be obtained from the unweathered strata in the cliffs. 



The greater part of my material was obtained from a small "table" about 

 twenty or thirty feet in diameter and sixteen to eighteen inches thick. The edge 

 of the table had been exposed by the wearing away of the face of the cliff, showing 

 two or three layers very rich in fossils. The overlying rocks were blasted out, 

 or worked out with pick and bar, as far as, and indeed farther than it was safe 

 to work into the face of the crumbling cliff. We apparently reached the inner 

 limits of the table,, and succeeded in removing practically all the specimens con- 

 tained in it. 



Some of the beds were crowded with fossil ferns and Bothriolepis, with here 

 and there a specimen of Scaumenacia, Holoptychius, and other fishes. The 

 animals in the richest beds were badly crushed, and the more delicate parts were 

 obscured by the abundant remains of plants and carbonized organic material. 

 In some of the other beds, where the rock was cleaner and more sandy, there 

 were fewer fossils, but they were not so badly crushed. In these layers there 

 were many specimens of Bothriolepis with the entire body distinctly preserved 

 in the attitude or position they were in at the moment they ceased to live. 



The table was no doubt at one time the bottom of a small seashore pool, or 

 inlet, in which shallow-water plants were growing. It was either invaded, at 

 pefiods of exceptionally high tides, by salt water that carried with it many fishes 

 and ostracoderms, or it was from time to time cut off from the main body of water 

 by shifting sand bars, or by similar causes. In either case, the animals trapped 

 in the enclosures soon died from the effects of the foul or superheated waters, and 

 were shortly afterward covered up and preserved by the shifting beach sands of 

 another invasion. 



The great majority of the specimens of Bothriolepis were found in a hori- 

 zontal position, ventral side down, and headed in the same direction, i.e., a little 

 north of east. These individuals evidently died in this position, oriented by some 

 common external agent. 



In nearly all such cases the slender trunk and tail extend in a straight line 

 backward, while the thin membranous dorsal and caudal fins, which were usu- 

 ally perfectly flat and fully expanded, stood in a vertical direction, i.e., at right 

 angles to the plane of stratification. The upright position of such delicate mem- 

 branes shows beyond question that these particular animals died quietly while 

 still in their natural positions. The fact that these animals were living partly 

 buried in mud or sand up to the time of their death, no doubt accounts for their 

 wonderful state of preservation. Side by side with them were other specimens 

 lying either on their back or side, with the dorsal fins and tail expanded in a hori- 



