540 DR WHEELTON HIND ON 



It differs from G. cymbaeformis of the Ludlow beds in the absence of ornament on 

 the valve below and in front of the strong oblique keel, and in being much less 

 transverse. 



Genus Grammysia, de Verneuil, 1847. 



Grammysia, de Verneuil, 1847, Bull. Soc. Geol. France, 2nd ser., vol. iv. p. 696. 

 Orthonota, pars, Salter, 1848, Mem. Geol. Surv. Gt. Britain, vol. ii., pt. i., p. 359. 

 Grammysia, Hall, 1885, Geol. Surv. Neiu York, Pal., vol. v., pt. i., Laniell., pt. ii. p. 30. 



Generic Characters. — Shell equivalve, closed. Lunule and escutcheon well 

 marked. Umbones anterior, and a compressed dorsal slope. Valves with an oblique 

 sinus from the umbo to the lower margin, often with an oblique fold. 



Interior. — Pallial line simple. Hinge plate edentulous. Adductor muscle scars 

 faint. 



Exterior. — Ornamented with concentric grooves and sulci, which become obsolete 

 on the dorsal slope. 



Observations. — Hall gives a long account of the relations of the genus, and 

 criticises Salter, who considered Grammysia as a subgenus of Orthonota. There can 

 be no doubt that the two genera are distinct. Salter considered Allorisma is a 

 synonym of Grammysia, and although the two genera are closely related, the former 

 has not the oblique fold and grooves which characterise Grammysia, and it has a 

 sinuate pallial line, so that it is expedient for both genera to be retained. Hall, 

 writing of Grammysia, states (op. supra cit.) : "Valves in the typical forms traversed 

 from the beak to the base by an oblique cincture and adjacent fold, which may be 



duplicate and are alternating in the two valves Some species show the cincture 



developed in the upper part becoming obsolete before reaching the margin. Many 

 forms show a broad cincture without an adjacent fold ; and in some species the cincture 

 is indicated by a line of slight interruptions or irregularities in the concentric 

 undulations ; other species have the surface continuous, without cincture or fold." I 

 have doubts if shells without the distinctive character of the genus should be any 

 longer retained in it. 



Grammysia undata, Sow., sp., 1839. (PI. V., figs. 13-16.) 



Cypricardial undata, Sow., 1839, Sil. Syst., p. 607, pi. v. fig. 3. 

 Orthonota „ Sow., 1859, Siluria, 3rd ed., pi. xxiii. fig. 4. 



,, ,, 1901, Fauna, Flora, and Geol. of Clyde Area, Brit. Ass. Handbook, p. 437. 



Specific Characters. — Shell of medium size, oblique, gibbose, very inequilateral, 

 subcarinate, transversely ovate. The anterior end is short and narrow, its margin 

 rounded. The antero-superior angle pointed. The inferior margin is markedly 

 convex, somewhat sinuous anteriorly. The posterior border is broadly obtuse below, 

 almost straight above. The hinge line is elongate and almost straight. The umbones 

 are large, prominent, raised, twisted forwards, inwards, and downwards, and anterior in 



