NATURAL HISTORY SOCIETY OF GLASGOW. 263 



Of the four ridges visible on the reverse (PI. V., fig. 9) the 

 two lateral ones appear to represent the boundaries of the pore 

 plates. The two inner probably form a portion of the lancet 

 plate, but, at times, in place of these four ridges, the two lateral 

 ones only are marked ; at others, the central ones are alone visible, 

 and represented by a groove (PI. V., fig. 11/), or open gutter, 

 extending the whole length of the ambulacrum. This mav answer 

 to the lancet canal of Mr. Rofe and other writers. 



Explanation of Plate V. (figs. 7-12). 



Fig. 7. — Pentremites, sp. — The best example yet found, showing- 

 portions of the basal plates ; portions of two of the radial plates ; 

 an entire radial or forked plate ; and one of the ambulacra. 

 Kidlaw, near Gilford, Haddingtonshire, from the Lower Carboni- 

 ferous limestone group. 



Fig. 8. — Front view of the best preserved ambulacrum — with the 

 ambulacral furrrow ; the pores leading to the inner depressions or 

 sockets (6) ; the outer sockets at the terminations of the branch 

 ambulacral grooves (c). 



Fig. 9. — Reverse of an ambulacrum, presumed to be that of the 

 foregoing species. Pores at the edges of the pore plates (6) ; 

 divisions of the plates (a) ; the four ridges (e). 



Fig. 10. — Side-view of another similar specimen, showing the 

 pores at the sides of the pore plates (6), and the outer depressions 

 or sockets in the same pieces (a). 



Figs. 11 and 12.— -Views of the reverse, in which the grooves 

 or gutters in the lancet plates (?) are visible (/). 



Figs. 9-12 are taken from specimens obtained at Carlops Quarry, 

 Carlops, Peeblesshire, from the shale above the Carlops limestone, 

 Lower Carboniferous limestone group. 



N.B. — The natural size of the specimens is shown by the indi- 

 cators. The originals of Plate V., figs. 7-12, are in the collection 

 of the Geological Survey of Scotland. 



IV. — Notes on Carboniferous Brachiopoda. By Mr. Robert 

 Etheridge, Jun., F.G.S., Pres. Royal Phys. Soc, Edinburgh. 

 Plates V. (figs. 1 to 6) and VI. 



1. On the colour markings in Lingula mytiloides (Sowerby), 

 Plate V., fig. 3. — The remains of colour bands have been noticed 

 in a few Carboniferous shells by De Koninck, Davidson, Young, 



