102 



OLD RED SANDSTONE FISHES. 



1855. Pterichthys ? cancriformis, M'Coy. Brit. Palseoz. Foss., p. 599. 



1855. 

 1855. 

 1880. 



1888. 

 1888. 

 1891. 



1891. 



productus, M'Coy. Ibid., p. 600. 

 oblongus, M'Coy. Ibid., p. 600. 

 Lahusen. Verb, russ.-kais. mineral. G-esellsch. [2] vol. xv, 



pi. ii, fig. a. 

 productus, Traquair. Geol. Mag. [3], vol. v, p. 509. 

 oblongus, Traquair. Ibid., p. 509. 

 productus, A. 8. Woodward. Cat. Foss. Fislies Brit. Mus., 



pt. ii, p. 217. 

 oblongus, A. 8. Woodioard. Ibid., p. 219. 



Specific Characters. — Distal segment of pectoral limb expanded on the inner 

 Fig. 54. Fig. 55. 



Fig. 54. — Diagram of the proportions of the under siirface of the body-carapace and left pectoral 

 appendage in a broad variety of Pterichthys ■productus. 



Fig. 55. — Diagram of the proportions of the under surface of the body-carapace and left pectoral 

 appendage in the narrow or "oblongus" form of Pterichthys productus. 



aspect. Contour of ventral aspect of carapace variable, sometimes comparatively 

 broad, more usually tending to assume a long and narrow appearance by a greater 

 lengthening of the posterior ventro -lateral plates in proportion to the anterior. 

 Carapace tending to be proportionately high as well as narrow. Surface ornament 

 as in Pt. Milleri. 



Description. — The peculiarity of the distal segment of the arm is seen in the 

 specimens figured in PL XXI, Figs. 1, 2, and 4, and in PI. XXII, Figs. 3 and 4. 

 The last mentioned figure is rendered specially instructive by being placed immedi- 

 ately under a drawing of the corresponding part in a typical specimen of Pt. Milleri, 

 whereby it is seen that though all the elements are in the present species 

 proportionately broader, this condition is most marked in the case of the outer 

 maro'iymls. 



