Dr. R. H. Tiaquair on Palceozoic Fishes. 369 



surface of the spine is otluu-vvise not well preserved ; but, so 

 far as one may judge from its condition, it shows no pecu- 

 liarity distinguishing it from the well-known Parexus recurvuSy 

 Ag., of the Forfarshire beds. 



The occurrence of Parexus in the west of England area of 

 the Old Red Sandstone has not, so far as I am aware, been 

 hitherto recorded, and is interesting as bringing out still more 

 strongly the resemblance between the Lower-Devonian tisli- 

 fauna of that region and that of the widely separated central 

 Scottish area. I may take the opportunity of stating here 

 that I have never been able to find any actual corroboration 

 of the alleged occurrence of Parexus in the Old Red of 

 Caithness. 



Coccosteidae. 

 Phlyctcenaspis anglica^ Traq. 



In my original description of this genus * I gave as one of 

 the marks of distinction between the two known species, 

 P. acadica, and P. anglica, that in the former the external 

 angle of the cranial shield was divided by a shallow notch 

 into two, the postero- and antero-external angles, whereas in 

 the latter these two angles were confluent and formed one 

 prominent postero-external projection. 



Cranial Shield of Phlyctcenaspis anrjlica, restored sketch (ethmoid 

 and pineal plates omitted). — m.occ, median occipital ; e.occ.y external 

 occipital : ag., angular ; c, central ; m., marginal ; jJi^.o., postorbital ; 

 p.o., prseorbital. 



That such a peculiar difference should exist between two 

 closely allied species seemed strange from the beginning ; but 

 light is thrown on the matter by a specimen of Phlyctcen- 

 * Geol. Mag. (3) vol. vii. 1890, p. 60. 



