OF THE AMEKICAN PTEEASPIDIAN, PALiEASPIS. 547 



In 1886, Mr. G. F. Matthew, of St. John, New Brunswick, 

 discovered near that town, in rocks of Upper Silurian age, a new 

 species of the family. In his paper on the subject, presented to 

 the New Brunswick Academy of Science, he published details 

 regarding it, making, among others, the important announcement 

 that in his opinion it was armour-clad ventrally as well as dorsally, 

 and giving satisfactory evidence in favour of this belief. This 

 species of Matthew's, named Biplaspis acadica from the character 

 above emphasized, which he then supposed to be peculiar to it, is 

 at present represented only by the single specimen in his own 

 possession — the basis of the original description. It was undoubtedly 

 the first instance on the American continent in which the existence 

 of a ventral as well as a dorsal armour on the Pteraspids was 

 announced. 



Mr. Matthew's fossil showed what he considered to be the frag- 

 ments of the dorsal and ventral shields of the fish, with a rostral 

 piece and two antero-lateral plates attached to the former and two 

 others (postero-lateral ?) attached to the latter. If Mr. Matthew's 

 interpretation of his specimen is correct, instead of the two 

 ' cornua ' of Lankester's Cyathasjois, Diplasjpis had four of these 

 side-pieces in its armour. Besides these, there was a separate small 

 plate, which its discoverer regarded as the eye-plate, and which 

 must in that case correspond to the eye-plate of Pteraspis, as that 

 genus is described by Lankester. In spite, however, of the resem- 

 blances, the fossil, judging from Mr. Matthew's description and 

 figures, which are, it is true, merely outlines, cannot be placed in 

 either of Lankester's three genera (really two), but must stand 

 alone, at least for the present. It may be well to observe that all 

 doubt and uncertainty respecting the correctness of the reference of 

 this fossil to the family of Pteraspidians is removed by the presence 

 on the shields of the peculiar and very characteristic striation, 

 whereby the smallest fragments of the defensive armour of these 

 fishes may be recognized with certainty whenever it is visible. 



Unfortunately, in this case the last crucial link in the argument 

 is imperfect. The two shields were not, as in Kunth's specimen, 

 found in position, and if the fossils were as abundant as they are 

 in many places in Europe and in Pennsylvania, this gap would be 

 serious. But in the circumstances obtaining in New Brunswick 

 the objection has but little weight. Only this one specimen has 

 ever been described from the Dominion of Canada, and the frag- 

 ments were found close together, so that Mr. Matthew's inference 

 that they belonged to one another cannot be refuted, or, indeed, 

 with good reason attacked. 



At the time of publishing his description of Diplaspis, Mr. Mat- 

 thew was evidently not acquainted with the latest results of 

 discovery in Europe on this subject, or with the papers above 

 quoted on the Pteraspidians. He consequently had not learned 

 that they were more than suspected to have been armour-clad above 

 and below. What doubt remained may be ascribed to the fact that 

 a new and unexpected discovery, and especially one which contra- 



