252 



Canadian Record of Science. 



plates ("cornua" ?) are preserved, as well as the front 

 half or third of the ventral shield ; the stria? on the ven- 

 tral scute are symmetrical in relation to a median line 

 passing through it ; there is a detached fragment of a plate 

 with concentric striae like the eye plate of Pteraspis ros- 

 trata. 1 There is also a large plate more strongly arched 

 than the ventral scute, on which the stria? are not arranged 

 with entire symmetry ; it appears to be the dextral half of 

 the dorsal plate ; it resembles the shield of Prof. Claypole's 

 Palcea&pis Americana in form, and in the linear stria? of the 

 border, but I can hardly think that it belongs to a different 

 individual from that to which the plates already described 

 pertain. On one side of this large plate is a small longitu- 

 dinally striated side plate, and on the opposite side the frag- 

 ment of another. 



Numbers of carapaces of a small Ceratiocaris occur on the 

 layers with the fish plates. The author is not aware that 

 the existence of a ventral shield has hitherto been observed 

 in any pteraspidian fish, although it is well known to exist 

 in the large Devonian placoderms ; the species is evidently 

 different from any other known, and he would propose 

 for it the name Pteraspis (J) Acadica. 



e-....-- e •... 



a. The infra-rostral plate. 



b. b. Anterior plates of the ventral shield. 



c. The ventral scute — a part only is preserved. 



d. The large oval plate — dextral half of the dorsal scute, seen 

 from below. 



e. e. Lateral plates of the dorsal shield. 

 /. Part of the eye-plate. (?) 



N.B. — The vertical dotted lines represent the median line of the 

 principal ventral plate and the supposed axial line of the half of the 

 dorsal scute. 



Quart. Jour. Geol. Soc, Feb. 1865, p. 62. 



