/. — Pleuracanthidce. 733 



Pleuracanthus undulatus, sp. nov. 

 (PI. LXXii., fig. 16.) 



Spine: straight, 0-13 m. in length, O'Ol m. in diameter at the base, gradually- 

 diminishing to the pointed apex. Section of spine, midway and higher, circular ; 

 base somewhat crushed, but apparently oval. UjDper posterior surface has two 

 rows of denticles, which are large, broad at the base, blunt and widely separated. 

 The denticles are placed diagonally, those of one row being slightly in advance 

 of those of the other. At a distance of 0-03 m. from the apical extremity, the 

 two rows are separated by a space equal to one-half the diameter of the spine, 

 and the interval between two denticles in the same row is 0-07 m. Both the 

 distances, between the two rows, and between the individual denticles diminish 

 gradually towards the point. 



This spine is clearly distinguished from others previously described, by the 

 large and widely separated posterior denticulation. It was found by Mr. George 

 Wild, of Bardsley, and presented to the Manchester Museum. 



Formation and Locality. — Thin-bed Coal, Fulledge Colliery, Burnley. 



Ex coll. — Mr. G. Wild : Manchester Museum, Owens College. 



Pleuracanthus tenuis, Davis. 

 (PI. LXXII., fig. 17.) 



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



vol. xxxvi., p. 327, pi. xii., fig. 1. 



Pleuracanthus tenuis, . . Etheridge, R., 1888, " Foss. Brit. Islands." 



Pleuracanthus tenuis, . . Woodward, A. S., 1889, " Cat. Foss. Fishes Brit. 



Mus.," pt. I., p. 10. 



Pleuracantlms tenuis, . . Woodward & Sherbgen, 1890, " Cat. Brit. Foss. 



Verteb.," p. 155. 



Spine: long and slender, imperfect; length preserved is 0'12m. ; diameter 

 0"005 m. ; basal part circular in section ; upper part more or less angular. 

 Along each lateral margin for a distance of 0'07m. there is a row of denticles, 

 about eighteen or twenty in number, with bluntly-rounded points tipped with 

 enamel. The spine is slightly curved. There is an internal canal, wide near the 

 base, but convei-ging higher up, and extending through the whole of the length. 



