60 Dr. R. H. Traquair— A New Genus of Coccosfeidce. 



fused or anchylosed together, and in the cast now under descrip- 

 tion the sutures are sometimes indicated by delicate raised 

 lines as in Ph. Acadicus. I have indicated in the sketch the 

 course of the divisions between the plates, naturally in a somewhat 

 exaggerated manner, as the lines themselves are only visible by a 

 lens and often cannot be followed at all. But from what is seen it 

 is quite clear that the plates were quite similar in general form and 

 arrangement to those in P. Acadicus, and especially to those in the 

 specimen represented in Fig. 2, the median occipital extending far 

 fowards and the centrals being rather truncated in front. 



One of the pencil outlines sent to me by Mr. Smith Woodward 

 shows apparently the rostral or ethmoidal plate in situ, thus com- 

 pleting the generic resemblance between the Canadian and English 

 species. 



We may therefore sum up the results of the preceding investiga- 

 tions as follows : — 



Genus PhJyctcenius, Traquair. Cranial shield more ovate than 

 in Coccosteus : constituent plates anchylosed, except the ethmoidal; 

 median occipital elongated, pointed in front and wedged in between 

 the posterior ends of the oblong or ovate central plates ; orbital 

 excavation looking more anteriorly than in Coccosteus ; course of 

 main lateral-line groove nearly straight from the external occipital 

 to the postorbital, where it is very acutely bent backwards. Plates 

 of body-cuirass imperfectly known. 



1. P. Acadicus, Whiteaves sp. External angle of cranial shield 

 divided by a shallow notch into two, the postero- and antero- 

 external angles ; surface ornamented by fine tubercles,, in most 

 specimens showing a concentric arrangement parallel to the margin 

 of the constituent plates. Lower Devonian, Canada. 



2. P. Anglicus, Traquair. Postero- and antero-external angles 

 confluent, surface covered by a coarse pustulation. Cornstones, 

 Herefordshire. 



In conclusion my most hearty thanks are due to Mr. Smith 

 Woodward for the information he has afforded me regarding the 

 Herefordshire specimens in the British Museum, and to Dr. Wood- 

 ward, F.R.S., for permission to make use of the plaster cast taken 

 from one of these specimens. 



EXPLANATION OF PLATE III. 

 In all the figures the same letters refer to the same things. 



P.L. postero-laferal angle. P.E. postero-external angle. A.E. antero-external angle. 



P.O. postorbital angle. A. 0. ante-orbital angle, m.o. median occipital, e.o. 



external occipital. c. central, m. marginal, pt.o. post-orbital, p.o. pre- 



orbital. e. ethmoidal. 

 Fig. 1. — Restored outline showing the arrangement of the plates and lateral-line 



grooves in the cranial shield of Ph. Acadicus, Whiteaves sp. 

 Fig. 2. — The same in another specimen, lateral margins of the shield restored in 



dotted outline. 

 Fig. 3.— Sketch of a specimen of the cranial shield of Ph. Anglicus, Traquair, from 



a specimen in the Edinburgh Museum. 

 Fig. 4.— Sketch of a plaster cast of another specimen, contained in the British 



Museum, the surface ornament being omitted. 



