ASTEROLEPIS MAXIMA. 75 



maintain the distinction of the two genera. This distinction lies in the mode of 

 articulation of the anterior median dorsal plate, which in Asterolepis ornata is 

 stated by Pander to overlap both anterior and posterior dorso-laterals, while in 

 Pterichthys it overlaps the anterior and is overlapped by the posterior of these 

 plates. The former mode of articulation I found extremely well marked iD a large 

 Asterolepid, the Coccosteus maximus of Agassiz from the Upper Old Red of Nairn, 

 and which I have since found to approach the Russian A. ornata in other, if more 

 trivial characters, more closely than it does the species referable to Pterichthys. 



My views have been adopted by Smith Woodward in his ' Catalogue,' so that 

 Asterolepis now stands out as a genus independent of Pterichthys, and repre- 

 sented in this country by one well-marked species, A. maxima, which I shall now 

 proceed to describe. 1 



Asteeolepis maxima, Agassiz, sp. Plates XV — XVIII. 



1845. Cocoosteus maximus, Agassiz. Poiss. foss. v. Gres rouge, p. 137, pi. xxxa, 



figs. 17, 18. 

 1848. Ptebichthys majoe, H. Miller (non Agassiz). Quart. Journ. Geol. Soc, 



vol. iv, p. 311. 

 1857. Asteeolepis, Pander. Placoderm. dev. Syst., p. 17. 

 1860. — oenata, Eichivald {pars, in errore). Leth. Rossica, vol. i, 



p. 1508. 

 1888. — maximus, Traquair. Geol. Mag. (3), vol. v, p. 568 ; and 



Ann. Mag. Nat. Hist. (6), vol. ii, 

 p. 494, pi. xviii, figs. 1, 2. 

 1891. — maxima, A. S. Woodward. Cat. Foss. Pishes Brit. Mus., 



pt. ii, p. 206, pi. v, fig. 1. 



Specific Characters. — Anterior median dorsal plate pointed-lanceolate in shape, 

 the anterior margin being very narrow ; obtusely carinated behind the middle. 

 Surface ornament consisting of small, very closely set tubercles with stellate bases, 

 rarely confluent, but sometimes arranged in rows, which are often concentric, 

 sometimes radiating, more often tortuous. Carapace and head attaining a length 

 of probably fourteen or fifteen inches in large specimens. 



Mr. Smith Woodward says of this species that it attains more than twice the 

 size of the Russian A. ornata, but I have seen plates and fragments which 

 indicate that the latter occasionally grew to a size as great if not greater than 



1 References to various doubtful fragments which have been assigned to " Asterolepis " will be 

 found in Mr. Smith Woodward's ' Catalogue,' pt. ii, p. 207. They are all foreign, with two 

 exceptions, namely, A. Malcolmsoni, Ag., and A. minor, Ag., which are said to have occurred in the 

 neighbourhood of Elgin (the latter also at Riga, in Russia), but without the original specimens it is 

 quite impossible to form any opinion as to their nature. 



