494 Dr. E. H. Traquair on the 



his figures or text ; but he makes one important statement 

 regarding the anterior median dorsal which demands atten- 

 tion, namely that its lateral margins have on the underside 

 narrow squamous surfaces which overlap both the anterior 

 and posterior dorso-laterals (" unter welche sich die beiden seit- 

 lichen Schilder 12 und 13 unterschieben "), a statement borne 

 out also bj his figures of the plates in question. Now we 

 have seen that in Pterichthys the anterior median dorsal plate 

 does not overlap the posterior dorso-lateral, but is certainly 

 overlapped by it, so that we have in this circumstance a quite 

 tangible mark of distinction between the two genera. 



1 have not seen the anterior dorso-median plate of Astero- 

 lept's ornatus ; but in the Upper Old Red Sandstone of 

 Nairnshire remains of a large Asterolepid are not uncommon 

 in which this plate certainly had the same relations to the 

 surrounding ones as Pander has described in the Russian 

 form. This is the Coccosfeus 7naximus oi' Ag^ssiz (4, p. 137, 

 tab. XXX a. figs. 17 and 18), who supposed the plate in question 

 was a median ventral, while Hugh Miller, with a better concep- 

 tion of its real nature, wished to consider it the dorsal plate of 

 ^^Pterichthys " major. Having now got together a very in- 

 structive set of its plates, I find that this creature is not Pte- 

 richthys 'major ^ which is in reality ixBothriolepis^ but a species 

 closely resembling the Pterichtiiys of the lower beds in all 

 essential respects save its depressed form and the mode of 

 articulation of its anterior median dorsal plate. In PI. XVIIL 

 figs. 1 and 2, I have given outlines of the upper and lower 

 aspects of this plate, the articular surfaces being shaded by 

 horizontal lines. There it will be observed that on the outer 

 aspect (fig. 1) there is no articular surface but the one, 

 2, at the posterior margin which is overlapped by the poste- 

 rior median dorsal, while on the under surface (fig. 2j the 

 antero- and postero-lateral margins show each a narrow sur- 

 face, X and ?/, which overlap the anterior and posterior dorso- 

 laterals respectively. Isolated specimens of tlie dorso-lateral 

 plates show corresponding surfaces on their outer aspects. 

 The rest of the creature, as I have said, resembles Pterichthys^ 

 but the carapace is more depressed, the anterior and posterior 

 dorso-lateral plates being narrower. The limbs are short and 

 are similar in construction to those of the last-named genus ; 

 and though I have seen little of the head, what I have seen 

 appears to correspond. As regards the tail, as no really 

 entire specimen of the creature has occurred, it is difficult to 

 speculate; but numerous rounded scale-like bodies occurring 

 in the same beds may possibly be referable to this part. 



1 therefore propose to refer this species to Asterolepi's under 



