738 Davis — On the Fossil Fish-Remains of the Coal Measures of the British Islands. 



Longton, Staffordshire ; Watston ; Stonehouse ; Newartliill ; Quarter Hamilton, 

 Scotland; Lowmain Coal Seam, Newsham, Newcastle- on-Tyne. 



Ex coll. — James W. Davis, Halifax ; Museum Literary and Philosophical 

 Society, Leeds ; John Ward, Longton ; James Thomson, Grlasgow ; Atthey Col- 

 lection, Museum Natural Hist., Newcastle-on-Tyne. 



Pleuracanthus erectus, Davis. 



(PI. Lxxm., fig. 14-16.) 



Pleuracanthus erectus, . . Davis, J. W., 1880, " Quart. Journ. Geol. Soc," 



vol. xxxvi., p. 326, fig. 2 (woodcut). 



Spine : length, 0-09 m. ; breadth at the base, 0-008 m., whence the sides converge 

 in straight lines to an elongated and acute point ; antero-posteriorly compressed ; 

 section oval, lateral margins produced, forming a series of convex, compressed 

 projections. The projections have a broad base and are widely separated from 

 each other. The surface of the spine is striated longitudinally. 



Since the description of the original specimen from the cannel coal at Tingley, 

 other specimens have been obtained from the same locality, which prove conclu- 

 sively that the similarity to Pleuracanthus Icevissimus, Ag., indicated in the original 

 descrijDtion,* and since emphasized by other authors,! "^^s only a generic one. 

 The species are quite distinct, and may be distinguished by the form and character 

 of the denticles very readily. In this species they are broad at the base and more 

 or less rounded, whilst in P. Icevissimus they are long, recurved, and sharply pointed. 

 The denticulated margin of the spine in the type specimen is 0'055 m. in length, 

 and on this margin there are twenty-two denticles ; in a specimen of Pleuracanthus 

 Icevissimus^ Ag., from the Lowmain coal, of a similar size and with the same 

 length of denticulated margin, there are thirty-seven denticles. This comparative 

 paucity of denticles in P. erectus is characteristic of all the specimens which have 

 come under observation. In shorter spines, which it is presumed were those of 

 younger fishes, the disparity is still more marked, and it is equally borne out by 

 larger ones. A very fine example (PL lxxiii., fig. 14), which is preserved, along 

 with others, from the Lowmain coal seam, in the Atthey collection, may be 

 compared with the specimen of Pleuracanthus Icevissimus, Ag. (PI. lxxii. , fig. 1), 

 from the same bed. In the latter there are sixty-five denticles on each margin, 



* Loc. cit., p. 326. 



f K. H. Traquair Proc. Koy. Phys. Soc. Edinburgh, vol. ix., p. 422 ; A. Smith Woodward, Cat. Foss. 

 Fishes, pt. i., p. 6 



