PARALLELODON ELEGANS. 135 



angular ridges, separated by wide concave sulci. Its ridges become crowded and 

 almost obsolete towards the flattened postero-supcrior angle. 



Dimensions. — Plate XXV, fig. G, a right valve, measures : — 



Antero-posteriorly ... 30 mm. 



Dorso-ventrally ... 40 mm. 



Locality. — In a marine band below the Gin mine Coal, Nettlebank Colliery, 

 Smallthorne, North Staffordshire. 



Observations. — Posidoniella sulcata occurs fairly abundantly in the marine band 

 associated with the Gin mine coal in the locality mentioned above. A list of the 

 fauna which has been recognised in this band was given supra, p. 121. The 

 character of the anterior end, the broad sulcations and angular ridges, at once 

 separate the shell from P. vetusta, with which species it is most nearly allied. It is 

 generically distinct from Posidonomya Becheri, with which I think it has probably 

 been confounded. I remember seeing a specimen in the collection of the late Mr. 

 James Nield, of Oldham, stated to be from the Middle Coal Measures. This was 

 named P. Becheri. It was flattened and crushed, and I made a sketch which 

 agrees very much with the character of P. sulcata. Mr. Gerrard has endeavoured 

 to trace Mr. Nield's shell for comparison, but has unfortunately not been able to do 

 so. Mr. H. Bolton ('Trans, and Ann. Rep. Manch. Micros. Soc, 1895') quotes 

 Posidonomya lateralis (a synonym of P. Becheri) as occurring in the Lower Coal 

 Measures of Lancashire. At Nettlebank P. sulcata occurs in all stages of growth 

 but seems to be confined to a narrow shale band near the base of the marine 

 deposit, which is itself only eleven feet thick. 



Parallec-odon elegans, M'Coy, sp., 1844. Plate XXIII, figs. 9, 10. 



Pullastra elegans, M'Coy, 1844. Synops. Carb. Foks. Ireland, p. 54, pi. viii, 



fig. 16. 



Specific ('ha carters. — Shell of medium size, ovate, subquadrate, moderately 

 gibbose, expanded posteriorly. The anterior margin is rounded, the lower border 

 slightly convex, the posterior border obliquely truncate from above, downwards and 

 backwards, almost straight, joining the lower margin with a blunt but regular curva- 

 ture, and making an obtuse angle above with the hinge-line. The latter is straight and 

 comparatively short. The umbones are moderately gibbose, placed in the anterior 

 third of the valve. The dorsal slope is rapidly compressed and is concave, bounded 

 below by a bluntly rounded oblique ridge, which arises at the umbo, and gradually 

 becomes obsolete as it crosses the valve. 



