PTBRIOHTHYR MTLLERI. 97 



1848. Ptebichthys quadratus, Sir P. Egerton. Quart. Journ. Greol. Soc, p. 313, 



pi. x, figs. 1 and 2. 



1848. — testudinarius, Sir P. Egerton. Ibid., p. 312. 



1849. cornutus, Sir P. Egerton. Ibid., p. 313. 

 1855. latus, M'Coy. Brit. Palseoz. Foss., p. 600. 

 1855. — testudinarius, M'Coy. Ibid., p. 600. 

 1855. — cornutus, M'Coy. Ibid., p. 600. 



1888. Milleri, Traquair. G-eol. Mag. (3), vol. v, p. 509. 



1888. — cornutus, Traquair. Ibid., p. 509, and Ann. Mag. Nat. 



Hist. (6), vol. ii, pi. xvii, figs. 1—3. 

 1891. Milleri, A. S. Woodward. Cat. Foss. Fislies Brit. Mus., 



pt. ii, p. 212, pi. v, figs. 1—7. 

 1891. — testudinarius, A. S. Woodward. Ibid., p. 216, pi. v, fig. 8; 



pi. vi, fig. 1. 

 1894. — Milleri, Traquair. Asterolepidse Pal. Soc, p. 65, figs. 34 — 36. 



1903. Asterolepis Milleri, Jaekel. Zeitschr. deutsch. geol. Gesellsch., 



vol. lv, Protokolle, pp. 41 — 60. 



Specific Characters. — Distal segment of pectoral appendage narrow and 

 tapering ; adult form having the flat ventral surface of the carapace rather broad, 

 the anterior ventro-lateral plate being equal in length to the anterior or only 

 slightly longer, and the distance between the posterior margin of the ventral 

 carapace and the centre of the median ventral plate being approximately equal to 

 the breadth of this part of the carapace at the point indicated. Narrower forms 

 (Pt. cornutus), however, occur, in which the shape of the ventral surface of the 

 body-carapace shows some approximation to that in the next species (Pt.prodnctiis), 

 the posterior ventro-lateral plates being proportionately longer and the breadth at 

 the median ventral plate somewhat smaller. The restored figures given in the 

 text at pp. 65 and 92 were taken from specimens of so-called " cornutus." 



Description. — PI. XIX, fig. 1, represents one of the best specimens in the 

 British Museum, which has already been figured by Dr. Smith Woodward in 

 his ' Catalogue.' It is of the type of Ft. latus (Ag.), which is evidently the adult 

 form of the small specimens figured by Agassiz as Pterichthys Milleri. Like the 

 great majority of specimens of this genus, it is compressed vertically, but, unlike 

 most, it shows the greater part of the dorsal surface of the body-carapace, that 

 aspect of the fish being ordinarily the one adherent to the matrix. The head 

 shows very little, with the exception of the pair of maxillary plates (mx.), which 

 are well seen in situ, the front portion of the cranial shield having become shoved 

 a little backwards. We note here the rounded notch situated at the posterior 

 external angle, instead of simply on the outer side as in Bothriolepis (see text- 

 figure, p. 112). The pectoral limbs are crushed, the left one in such a manner as 

 to obscure the slender and tapering form of the distal segment. The median dorsal 



