542 DR WHEELTON HIND ON 



rest of the valve by an erect angular ridge. Passing from the umbo to the inferior 

 border at the junction of the anterior and middle thirds of the valve is a deep, broad, 

 oblique sulcus, becoming more marked as it approaches the margin. Posterior to this 

 groove the shell is obliquely gibbose. The dorsal slope is rapidly compressed and 

 hollow. 



Interior. — The anterior adductor muscle scar is very large and» placed close to the 

 anterior margin. The posterior is inconspicuous ; pallial line entire. 



Exterior.— Apparently ornamented with concentric lines and striae of growth. 



Dimensions. — Fig. 12, PI. V., measures : antero-posteriorly, 35 mm. ; dorso- 

 ventrally, 16 mm. ; from side to side, 16 mm. 



Locality. — The Star-fish bed, Upper Bala. 



Observations. — A single specimen of this shell has been collected. It has many 

 resemblances to G. cingulatus, Salter, but is at once separated by the absence of 

 oblique ribs in the left valve and much shorter anterior end. The specimen which I 

 figure is, however, the cast of the interior, and it is possible that the exterior of the 

 valve had characters not indicated in the internal cast. 



Grammy sia graridis, sp. nov. (PI. V., figs. 11, 11a.) 



Specific Characters. — Shell of moderate size, transversely rhomboidal, gibbose, with 

 well-marked oblique ridge separating a compressed and hollowed dorsal slope from the 

 rest of the valve. The anterior end is very short, curiously compressed by an 

 oblique sulcus, its margin rounded. The inferior border is long, marked in the 

 anterior half by two sinuations, nearly straight. The posterior border is nearly 

 straight, obliquely truncate above, bluntly rounded below. Postero-superior angle 

 well marked, obtuse. The hinge line is almost straight and long, parallel with the 

 lower border. 



The umbones are obtuse, continuous with the border of the lunule in front, so that 

 they appear to be continuous with the anterior border, incurved, contiguous, placed far 

 forwards, deeply grooved by the deep sulcus, which passes downwards and somewhat 

 backwards to the lower border. Lunule large ; escutcheon elongate and shallow, its 

 margin a bluntly rounded ridge. 



Interior. — The adductor muscle scars are very inconspicuous. Pallial line appears 

 to be entire. 



Exterior. — The surface is ornamented with concentric ridges and sulci, somewhat 

 irregular in size, which become almost obsolete on the dorsal slope, and are interrupted 

 by the two oblique grooves on the surface of the valve. 



Dimensions. — Fig. 11, PI. V., measures : antero-posteriorly, 65 mm. ; dorso- 

 ventrally, 33 mm. ; transversely, 33 mm. 



Locality. — The Star-fish bed, Upper Bala. 



Observations. — This is a large and beautiful shell, closely resembling the Allorisma 



