PTERICHTHYS PRODUCTUS. 101 



specimens of Pt. Milleri. The original of Fig. 5 shows the unmistakable pectoral limb 

 of Pt. Milleri, though the ventral aspect of the body-carapace is of a slightly narrower 

 contour than that in the ordinary form of that species. But the specimen from 

 which Fig. 4 was taken shows at the first glance the shape of carapace charac- 

 teristic "of the oblongus form of Pt. productus, and, the previously hidden terminal 

 portion of the pectoral limb having been, with Dr. Smith Woodward's authority, 

 uncovered, the identification with "productus" was proved by the expanded form 

 of the part in question. The specimens figured by Dr. Smith Woodward in his 

 ' Catalogue' (Pt. ii, PI. V, Fig. 8, and PI. VI, Fig. 1) as Pt. testudinarius come, how- 

 ever, by the tapering pectoral limb, and the comparative narrowness of the ventral 

 surface of the carapace, under the type of "cornutus" as exemplified in Agassiz' 

 PI. II, Fig. 5. 



Pt. quadratus (Egerton). — Like Dr. Smith Woodward, I fail to see any tangible 

 distinction between this supposed species and the broader form of Pt. Milleri. 1 



Geological Position and Localities. — In the Middle Old Red or Orcadian 

 Series of Orkney, Caithness, and the Moray Firth area : 



Orkney .- In the Stromness Beds, but not common. Caithness : Common in the 

 beds worked at Achanarras Quarry, near Spital and about ten miles south of 

 Thurso. But it seems to be absent from the Thurso Beds, as well as from those 

 at John o' Groats, which latter yields the small Asterolepid named by me Micro- 

 brachius Dicki. Moray Firth : In limestone nodules at nearly all the fish-bearing 

 localities of the Orcadian Old Red in this region, but especially at Cromarty, Lethen 

 Bar, and Gamrie. Edderton and Tynet Burn may also be mentioned, though it 

 occurs less frequently in these localities than in the others previously named. 



Pterichthys productus, Agassiz. Plates XXI and XXII, figs. 3 and 4. 



1844. Pterichthys productus, cancriformis (pars.) and oblongus, Agassiz. 



Poiss. Foss., vol. ii, pt. i, p. 302 

 (names only). 

 1844. — Agassiz. Poiss. Foss. v. grcs rouge, p. 10, pi. v, 



figs. 1 — 4. 

 1844. — cancriformis, Agassiz. Ibid., pi. i, fig. 4, non fig. 5. 



1844. — oblongus, Agassiz. Ibid., pi. iii, figs. 1 and 2. 



1844. — cornutus, Agassiz. Ibid., pi. ii, fig. 4, non figs. 1, 2, and 5. 



1848. — productus, Sir P. Egerton. Quart. Jonrn. Geol. Soe., 



vol. iv, p. 312. 

 1848. — oblongus, Sir P. Egerton. Ibid., p. 313. 



1 Dr. Smith Woodward in his " Catalogue," pt. ii, p. 212, gives the "Geological Society of London" 

 as the location of the type of Egerton's " quadratus." I could not find the figured specimen in thai 

 collection, but there is one there, labelled in Sir Philip's handwriting "Pterichthys quadratus," which 

 is certainly referable to " Milleri." 



