1. — PleuracanthidcB. t4:5 



recurved, acuminate denticles, forty-five in number. The surface of the spine 

 is smooth or slightly striated. 



This species is most nearly related to P. Icevissimus, Ag., but the position of the 

 denticular row is not lateral but is placed far towards the posterior surface as shown 

 in fig. 21a; the denticles are more hooked than in P. Icevissimus. 



The rows of denticles are, however, not nearly so closely approximated as in 

 P. eylindricus ; they appear to show a connecting and intermediate link between 

 the two species, and go a long way to prove their generic identity. I have 

 appended the specific name Woodwardi in recognition of the services of my friend 

 Mr. A. Smith Woodward. 



Formation and Locality. — Coal Shale, Dalkeith. Candenfoot, Dalkeith. 



Ex coll. — No. P 3178a. Enniskillen Collection, Natural History Department, 

 British Museum. No. P 1730. Egerton Collection, Natural History Department, 

 British Museum. 



Pleuracanthus (Lopliacantlius) Taylori, Stock. 

 (PI. Lxxiii., figs. 22, 23.) 



A spine from Airdrie (No. 42,035 in B. M. Coll.), perfect at the proximal end, 

 but wanting the distal one, is 0*20 m. in length. It is slightly curved, 0-01 m. in 

 diameter at the widest part, more or less circular in section, the antero-posterior 

 diameter being greater than that between the sides, with a double row of denticles 

 extending along the posterior surface to a distance of 0*07 m. of the base. The 

 denticles are short, rather widely separated, slightly curved backwards. The 

 rows of denticles are separated by a distance equal to half the diameter of the 

 spine between the anterior and posterior surfaces. The surface is smooth or 

 slightly ridged in wavy lines. The proximal extremity is rounded with the 

 terminal orifice open for a short distance along the posterior surface. The 

 internal cavity higher in the spine is small. 



This spine closely resembles that of P. cijlindricus, Ag., but has a more distinct 

 curvature than the spine of that species, and is more especially distinguished by 

 the wide area separating the two rows of posterior denticles. 



The spine. No. P 42,035, appears to be closely related to a spine from the Low- 

 main Coal Seam at Newcastle, at present in the Atthey collection in the Museum of 

 Natural History. The Newcastle specimen is 0-24 m. in length, and is slightly 

 thicker than the one in the British Museum, but in other respects is characterized 

 by its curved outline and the position of the two rows of denticles (fig. 23). 



5 Q2 



