396 Annals of the Sonth African Museum. 



cast of the complete shell, and the other shows the surface of the 

 left valve. The description of this new form is as follows : — 



Shell elongated-elliptical, nearly twice as long as high, strongly 

 tumid in middle, slightly compressed behind, not gaping at posterior 

 end. Anterior end short, narrower than posterior end, acutely 

 rounded. Posterior end broader, obtuse, rounded, subtruncate 

 above. Dorsal margin straight behind beaks. Hinge-line edentu- 

 lous, shorter than shell, with faint narrow lanceolate escutcheon. 

 Ventral margin nearly straight for three-fourths its length, with very 

 weak broad shallow excavation near middle. Beaks situated at 

 about one-third the length of shell from anterior end, large, obtuse, 

 broad, rounded, swollen, directed forwards and incurved, rising 

 above hinge-line, and overhanging a large, slightly depressed cordi- 

 form lunule. Umbonal ridge broad, swollen, undefined. Anterior 

 slope of shell steep, rising rather suddenly from margin, rounded ; 

 median portion of valve rather flattened, particularly near weak 

 excavation in ventral margin ; post-umbonal slope somewhat 

 flattened. Surface marked with weak corrugations and strong con- 

 centric growth-lines. Pallial line entire. Muscular scars almost 

 obsolete. 



Dimensions. — Length 48 mm. ; height 28 mm. ; thickness 

 25 mm. 



Remarks. — This species is undoubtedly allied to Grammysia luncli 

 Clarke,* but as to its precise generic position there would be some 

 doubt if we rejected the name LejJtodomus, as "Wheelton Hind f 

 seems inclined to do. Whidborne,:|: however, has kept it for certain 

 Devonian shells, one of which, L. constrictus McCoy, § bears a con- 

 siderable resemblance to our shell. Beushausen's || usage of the 

 generic names Lcptodomus and Allerisma does not commend itself 

 to Wheelton Hind, and the whole of the generic group of the Gram- 

 mysiidee seem to require revision. G. luncli is a much shorter shell 

 than ours, and has higher beaks, more anteriorly situated. The 

 shell figured by Kayser 1l from the Devonian of Argentina as 

 Leptodomus sp. bears some resemblance to this South African 

 species. 



* Clarke, op. cit., p. 6(5, pi. vi., figs. 11-13. 



t Wheelton Hind, Brit. Carb. Lamellibr. (Palseont. Soc), parts 3-5, 1898-1900, 



pp. 228, 379, 419. 



+ Whidborne, Mon. Brit. Dev. Fauna, vol. iii., pt. i., 1896, p. 74. 



§ Whidborne, oj). cit., p. 75, pi. viii., figs. 8, 9. 



II Beushausen, op. cit., pp. 250, 263. 



•i Kayser, Zeitsehr. dent. geol. Gesell., xlix., 1897, p. 289, t. x., fig. 6. 



