NATURAL HISTORY SOCIETY OF GLASGOW. 93 



mantle have rounded bases, and do not appear to possess processes 

 of attachment. 



I have not been able to meet with any described species of fossil 

 Chiton, which would include these little plates. They must, 

 therefore, so far as my researches have gone, be looked upon as 

 undescribed, an opinion in which I am glad to have the support of 

 Mi. Kirkby. Chiton mempiscus, de Kyckholt, is somewhat like in 

 outline, but is much shorter. I therefore propose for them the 

 specific name of C. solaeformis, in allusion to their resemblance to 

 an open slipper or shoe, when viewed from one side. 



Locality and Horizon. — Law Quarry, near Dairy, as before. 



Cot ted ion. — J. Bennie. 



Chiton contain*, Kirkby.— (PL I., figs. 20-22.) 



C. cordatus, Kirkby, Quart. Jour. Grot. Soc, 1859, xv., p. 66, 



t. 16, f. 25-26. 

 Kirkby, Trans. Tynedde Nat. Field Ctub, 1860, iv., 



p. 250. 

 ,, Kirkby and Young, Geol. Mag., 1867, iv., p. 341, 



t. 16, f. 10 a and h, 11 a and //. 

 Sjj. Char. — Posterior plate acutely cordate, acuminating pos- 

 teriorly to a sharp point. Median line arcuate, the angulation 

 being moderately acute. The dorsal area is defined by two sub- 

 parallel ill-marked grooves, which proceed forwards from a point 

 about half way between the posterior apical termination and the 

 front margin. Posterior margin of plate a little flattened ; the 

 anterior margin is indented in the middle line, the indention being 

 caused by the projection of the two small and delicate apophyses. 

 Surface ornament consists of granules arranged in transverse, and 

 not concentric lines, no grooving of surface present. Viewed from 

 the interior the plate is seen to be of considerable thickness 

 towards the posterior, forming a smooth triangular surface of 

 attachment destitute of markings of any kind. The dorsal area in 

 its convexity, and the character of the defining sulci (here ridges) 

 are much more marked than on the exterior. 



Obs. — Except in a few trivial points the plates I have repre- 

 sented in Figs. 20-22 do not differ from Kirkby's Chiton cordatiis, a 

 Permian species. The Carboniferous form appears to differ only 

 in possessing a more acutely cordate form, absence of transverse or 

 concentric sulcations, and the position of the sulci defining the 



