478 Reviews — J. W. Evans — N.E. Caithness. 



named Pygopterus Bonnardi by Agassiz, not hitherto described. It 

 is gratifying at last to have a good figure and description of the 

 fossil to which this name refers ; but we fail to recognize the 

 slightest resemblance to Pygopterus, and until Dr. Sauvage is able to 

 bring forward further evidence on the subject, we shall continue to 

 believe that P. Bonnardi is founded on part of the caudal region of 

 a Pleuracanth Elasmobranch. 



Of the Dipnoan fish described by G-audry as Megapleuron Bochei, 

 and of the Pleuracanth spine named by the same author Pleur acanthus 

 Frossardi, Dr. Sauvage merely reproduces the original descriptions 

 and figures. No allusion is made to Dr. Anton Fritsch's observations 

 on Megapleuron, in which the rhomboidal scales are correctly, 

 as we consider, assigned to a fragmentary Palgeoniscid mingled 

 with the skeleton. This correction is of importance, for it enables 

 "Megapleuron" to be recognized as a typical Sirenoid Dipnoan. 



There is now hope that Dr. Sauvage's long-promised memoir on 

 the Palseoniscid fishes of the Coal-measures of Commentry will not 

 much longer be delayed ; and we await with interest the further 

 contribution to our knowledge of this intricate group of fishes. 



A. S. W. 



VI. — The Geology of the Noeth-East op Caithness, and a Dis- 

 cussion AS to the Age of the Old Eed Sandstone of the 

 North of Scotland. By John Williams Evans, LL.B., B.Sc, 

 F.G.S. Pp. 48, with Sketch-Map. (London : Green, McAllan 

 and Feilden, 1891.) 



IN this pamphlet the author gives us the result of six weeks' 

 field-work in Caithness. The county is occupied almost entirely 

 by the Old Eed Sandstone with coverings of Glacial Drift ; it is to 

 the older formation that attention is now directed. 



Murchison divided the Old Red Sandstone of Scotland into three 

 portions : the Lower, including the Arbroath flags, with Cephalaspis, 

 Pteraspis, and Pferygotus ; the Middle, including the Caithness flags, 

 with Osteolepis, Asterolepis, Pterichthys, etc. ; and the Upper, in- 

 cluding the Dura Den beds, with Pterichthys, HoloptycMus, etc. 



Sir Archibald Geikie afterwards referred the Caithness flagstones 

 to the Lower Old Red Sandstone, and maintained there was no 

 evidence of any Middle division. 



The observations of the author lead him to maintain that the 

 Old Red Sandstone of Caithness belongs entirely to the Upper 

 division ; and he thus represents the succession of the Scottish 

 Upper Old Red Sandstone : — 



'■ _» (Sub -zone of Bothriolepis hydrophila, ) _ _ 



! |s I Holoptychms Flemingi, and Glypto- i Dura Den, etc. 



H O 



^ S 



I Moloptychius ±lemingi, and h-lypto- t 

 J pomus minor. ' 



t° I Sub-zone of HoloptycMus nobiUssimus g^^^ ^^.^j Clashbennie, etc. 

 f§ and Cricodus favosus. \ 



a r Sub-zone of Mierobrachius Dicki and Tristichopterus alatus. 

 •^ J Caithness Flags, Orkney and Shetland beds, and the Old Red Sand- 

 g 1 stone of Cromarty, Gamrie, etc. 

 (^ Basement Conglomeratic series. 



