from the Neighbourhood of Edinburgh. | 259 
teeth and scales, which it is difficult to obtain from those pre- 
served in the refractory ironstone of the Wardie nodules. 
In his very brief notice of this fish* Agassiz stated that, 
though very distinct as a species, its generic relations were 
doubtful, mentioning as a reason that the scales were much 
higher than broad. Having, since my previous description was 
written, enjoyed better opportunities of studying the characters 
of the genus Pygopierus, [ have found the conclusion inevit- 
able, that Agassiz’s doubts were so well founded that it be- 
comes absolutely necessary to erect a new genus for the fish 
under consideration. I propose, then, for it the generic title of 
Nematoptychius, in allusion to the fine thread-like strie with 
which the scales and many of the head-bones are ornamented. 
As regards the scales, these differ in a most marked manner 
from those of Pygopterus. In the latter genus they are 
regularly rhomboidal (Pl. XVI. fig. 6); and over the greater 
part of the body they are equilateral, those in the front of 
the flank only being rather higher than broad. ‘The exposed 
rhombic surface has its acute angles pointing, as usual, up- 
wards and forwards, downwards and backwards ; the anterior- 
superior angle is produced into a prominent point covered by 
the adjoining scale ; while from the middle of the upper margin 
a special and well- marked articular peg or spine likewise rises, 
to be received into a corresponding depression on the under sur- 
face_of the scale above. In fact Agassiz describes the scales 
of P. mandibularis as being very firmly articulated by means 
of ‘‘ deux cornes, qui existent au bord supérieur de V’écaille, et 
se logent sous la surface émaillée de l’ecaille voisine” t. These 
‘“deux cornes” (the one a production of the anterior-superior 
angle of the scale, the other a special articular spine arising 
from. its upper margin) are indeed, as every one knows, by 
no means specially characteristic of P; ygopterus. In Nema- 
toptychius Greenockii, however, the scale is of a very dif- 
ferent and, in truth, "most peculiar form (Pl. XVI. fae 9, 
EO vit). All along ‘the back and flanks the scales are much 
higher than broad ; the exposed area is indeed more or less 
rhomboidal ;_ but the acute angles are here the posterior- 
superior and the anterior-inferior. The anterior-superior 
angle is not produced into an articular point, distinct from 
the proper articular spine, which latter, broad and triangular, 
arises from the entire upper margin of the scale. ‘The ex- 
posed ganoid surface is ornamented by very delicate thread- 
like, wavy, branching and anastomosing ridges, which, in the 
* Poissons Fossiles, t. 1i.-pt. 2, p. 78. 
+ Ibid. p. 76. 
