244 



Shell or shells either single and separate or aggregated into clusters 

 of two or three individuals : relative convexity of the two valves varia- 

 ble : shape irregular. Lower valve shallowly convex ; upper valve 

 usually flatter and sometimes a little concave. Lateral outline variable 

 in different individuals, no two being alike : as a rule though the single 

 specimens are higher than long, and the clustered individuals are longer 

 than high, while the narrowest part of the valves in all is, as is custom- 

 ary in the genus, at the short hinge line. Thus, of the single or separate 

 specimens some are narrowly elongated in the direction of their height, 

 their dorso-ventral diameter being nearly twice as great as that from 

 the buccal to the anal side, and the two sides are nearly parallel, while 

 others are more or less triangular in their contour and widen out gra- 

 dually towards the pallial border, though in these also the dorso-ventral 

 diameter somewhat exceeds the maximum length. In clustered speci- 

 mens, on the other hand, the valves often expand broadly, irregularly 

 and laterally at a short distance from the hinge line, and the buccal 

 margin is broad and nearly straight : in such individuals the length 

 is nearly twice as great as the maximum height, and the greatest length 

 is a little below the middle, as in the original of fig. 1 on plate 32. 



Muscular scar large, reniform or subovate, situated near to the buccal 

 margin and about halfway between the cardinal and pallial borders. 



Surface markings consisting apparently of coarse and irregularly 

 disposed concentric lines of growth. 



Skidegate Inlet, south side of Alliford Bay : two single and two clus- 

 tered specimens. Skidegate Inlet west of Alliford Bay, J. Richardson, 

 1872: three separate specimens. 



The affinity of these oysters is obscure, as the range of variation of 

 the species to which they belong has yet to be ascertained. For the 

 present, however, it will be convenient to designate them by a local 

 and temporary name. 



GRYPH^EA NEBRASCENSIS, Meek and Hayden. 

 Plate 32, figs. 2, 2a, and 26. 



Gryphcea calceola, far. NebrascensiSfM. & H. 1861. Proceedings of the Academy 



of Natural Sciences of Philadel- 

 phia, VoL xiii. p. 437. 

 1865. Palaeontology of the Upper 

 Missouri, p. 47, pi. 3, figs, la-e, 

 and woodcuts A.B.C.D. 



" " Whitfield. 1876. Palaeontology of the Black 



Hills of Dakota, p. 349, pi. 3. figs. 

 13-16. 



(Perhaps a variety of Gryphcea resiculosa, Sowerby. 



