528 DR WHEELTON HIND ON 



plate, dividing off the exterior adductor muscle scar from the rest of the valve. 

 Surface smooth or not fine concentric lines of growth. 



Observations. — Hall's name is prior to any others, and must stand. M'Coy 

 (op, supra cit.) says: "King's genus Pleurophorus, I find from examination of 

 authentic specimens to be exactly equivalent to Clidophorus." This surely must be 

 an error, as Pleurophorus is a shell with a well-marked hinge plate which has strong 

 cardinal teeth, and does not possess the peculiar form of internal plate described by 

 Hall in Clidophorus. Cucullella, M'Coy, 1848, and Nuculites, Conrad, 1841, probably 

 synonymous, denote a genus which, although it possesses the clavicular plate of 

 Clidophorus, has a multidenticulate hinge, and therefore must differ from that genus. 



Clidophorus planulatus, Conrad, sp., 1841. (PI. IV., fig. 15.) 



A T ueulites planulalus, Conrad, 184-1, Ann. Rept., p. 48. 



Cleidophorus „ Hall, 1847, Pal. New York, vol. i. p. 300, pi. lxxxii. figs. 9a-e. 



Clidophorus „ M'Coy, 1855, Brit. Pal. Foss., p. 273, pi. i. k. fig. 9. 



Specific Characters. — Shell subelliptical, very moderately convex, broader in front 

 than posteriorly. Anterior margin elliptical, inferior slightly convex, posterior 

 obliquely truncate or bluntly curved. Hinge line somewhat arcuate. Umbones 

 small, incurved, pointed, placed immediately in front of the centre. Valves uniformly 

 curved. 



Interior. — Immediately in front of the umbo is a fine oblique rib, which leaves a 

 groove in casts, which extends one-third the distance across the valve. 



Exterior. — Surface almost smooth. 



Dimensions. — Fig. 15, PI. IV., a left valve, measures : antero-posteriorly, 11 ram. ; 

 dorso-ventrally, 8 mm. 



Localities.- — Scotland : Middle Bala Beds, Shalloch Mill. Wales : Golden Grove, 

 Llandeilo. 



Observations. — A single example of this species occurs in the Gray Collection, from 

 the Middle Bala. It shows the characteristic process in front of the umbo, which 

 distinguishes the genus. Nucidites also has a similar process, but in this genus 

 the hinge is furnished with numerous transverse narrow teeth, of which 1 can see 

 no trace in the Scotch specimen. The species is not uncommon in the Utica Slate 

 and Hudson River group of North America. M'Coy has recorded the species 

 from Llandeilo. 



Genus Cardiomorpha, de Koninck, 1842. 

 For synonymy, see Hind, Carboniferous Lamellibranehiata (Pal. Soc), 1898, p. 256. 



Generic Characters. — Shell equivalve, inequilateral, gibbose, of obliquely rounded 

 or Bubquadrilateral shape. The umbones are swollen and elevated, with the beaks 



