THE LOWER DEVONIAN EISHES OF GEMtJNDEN. 733 



the median and external occipital plates. Behind this, the space which ought to have 

 been occupied by the median dorsal is of course blank, but at the sides we have evidence 

 of the lateral plates of the body-cuirass, though hardly in a condition for accurate 

 description. Lastly, on the right side of the hinder part of the cuirass is seen the inner 

 surface of the displaced median dorsal plate, which for obvious reasons is not so extensively 

 worked out as on the outer aspect. It shows, however, very distinctly the downwardly- 

 projecting median process, which attains so large a development in Coccosteus decipiens, 

 and in Homosteus is represented by the " nail "-like process of Hugh Miller. 



Observations. — This is undoubtedly a true Coccosteus, and one of the oldest known 

 species of the genus, two other Lower Devonian species being 0. occidentalis, Newb., 

 from the Corniferous of North America, and C. hercynius, H. von Meyer, from the 

 Harz. The genus is therefore of wide geological range, as, besides being abundantly 

 represented in the Middle Old Red Sandstone (Orcadian series) of Scotland, a species 

 (C. Canadensis, A. S. Woodw.) has been found in the Upper Devonian of Canada, 

 another (C magnus, Traq.) in the Scottish Upper Old Red, and a third (C. disjectus, 

 A. S. Woodw.) in the Upper Old Red of Ireland. The present species is distinguished 

 from all others by the crest on the median dorsal plate. 



Genus Phlyctcenaspis, Traquair. 



Phlyctenaspis Germanica, Traquair. PL I. fig. 4. 

 Phlydttmaspis Germanica, Traq., Proc. Brit. Assoc, Belfast, 1902, p. 263. 



In fig. 4, PI. I., we have what appears to me to be the median portion of the cephalic 

 shield of a species of Phlyctcenaspis from the rostral plate in front to the posterior 

 margin of the median occipital behind, but wanting the lateral portions to which the 

 postorbital, marginal, and external occipital plates so largely contribute. That the 

 lateral parts have been broken away is rendered certain by the fact that a portion of 

 the posterior part of the outer margin of the shield still remains on the right side, and 

 is seen to be joined behind to the occipital region. 



No sutures are visible, but there are certain indications of the contour of rostral and 

 pre-orbital plates similar to those of Ph. Anglica, Traq. # The posteriorly directed sen- 

 sory groove on each central plate is also indicated, though the exact demarcation of the 

 plates themselves cannot be deciphered. 



The surface, where intact, is covered with stellate tubercles, which in proportion are 

 much smaller than in Ph. Anglica, Traq., and not so closely placed as in Ph. Acadica 

 (Whiteaves). 



* R. H. Traquair, Geol. Mag. (3), vol. vii., 1890, pi. iii. figs. 3, 4. Ann. and Mag. Nat. Hist. (6), vol. xiv., 1894 

 p. 369, woodcut. A. S. Woodward, Gat. Foss. Fishes, Brit. Mus., Pt. ii., pi. viii. figs. 5, 6. 



