744 Davis — On the Fossil Fish-Remains of the Coal lleasures of the British Islands. 



Pleuracanthus serratus, sp. nov. 

 (PI. Lxxiii., figs. 19, 20.) 



Spine : length averages 0*04 ; the longest example is 0'07, and the shortest 

 0'015. An example 0'04 in length is 0"002 in diameter at the base, and diminishes 

 to a fine point at the distal extremity. The anterior surface is more or less circular 

 in a section cut across the spine ; the posterior surface is also rounded but to a 

 smaller extent. A double row of denticles, twenty in number on each side, extends 

 along the lateral posterior sui-face in the position shown in fig. 19. The denti- 

 culated surface "extends from the point a distance of 0"025 m. towards the base. 

 The denticles present the appearance of a series of triangular pendants, the point 

 of each being suspended from the base of the preceding one ; they are closely set, 

 and the base, at its lowest and widest part, is equal in width to the height of the 

 apex of the wedge-shaped denticle. The denticles are largest midway, and 

 decrease in size both towards the distal and basal extremities. 



A considerable number of these small spines have been obtained from the Low- 

 main Coal Seam. The posterior position of the denticles at once distinguishes 

 them from small examples of Pleuracanthus la;pissimus, Ag., which frequently occur 

 in the same beds about the same size. The number of denticles is equal to that 

 of P. robustus when full grown, but their form is sufficiently distinctive, and they 

 do not fall in with any of the previously described species. 



Formation and Locality. — Lowmain Coal Seam, Newsham. 



Ex coll. — Atthey Collection, Museum of the Natural History Society of North- 

 umberland and Dm'ham at Newcastle-on-Tyne. 



Pleuracanthus Woodwardi, sp. nov. 

 (PI. LXXIII., fig. 21.) 



Spine: length 0*25 m.; point and base imperfect; probably 0-025 must be 

 added at distal end, equal to 0'275 m. without addition to base, or 0"3 in length 

 if complete ; base crushed ; at a distance of 0*1 m. from proximal extremity the 

 diameter is 0*015 m., from which point it tapers to the distal end. In section the 

 spine is oval, with a flattened anterior surface. The posterior surface has a slight 

 median ridge, and on each side, extending a distance of O'l m. on the part 

 preserved (or probably 0"12 m. if it were perfect), there is a row of large, 



