20 UNITED STATES GEOLOGICAL SURVEY OF THE TERRITORIES. 



< ■ i- j j> E i :v ; i vesicular is, Lam. ? 



Plate 11, ligs. '2,11, 6, c; and pi. 16, ligs. 8, a, b. 



Oslrea deltoidea (part), Lamarck (1806), Ann. Mns., VIII, 160 ; and XIV, 375, 21, pi. fig. 3. 



Ostrea vesieularis, Lamarck (1806), ib., VIII, 160, pi. 22, fig. 3 ; and (1819), Hist. An. Sans Vert., VI, 219.— 



Goltlf. (1826), Petrel'. Germ,, 1,23, tab. 81, fig. 2.— Dcshayes (1830), Encyc. Metli., II, 



292.— D'Arckiac (1837), Mem. Soc. Geol., II, 183.— Bronn (1837), Letk., tab. 32, fig. 



1.— D'Orbiguy (1843), Palaeout. Fr., Ill, 742, pi. 4s7, figs. 1-2 (excl. figs. 6, 8, and 9). 

 Oslraites mi/sticus, Schloth. (1813), Tasc, VII, 112. 

 Podopsisgryphoid.es, Lamarck (1819), Hist. An. Sans Vert., VI, 195. 

 GrypHtes truncates, Schloth. (1820), Petref., 289. 

 Oslrea convexa, Say (1820), Am. Jonr. Sci. and Arts, II, 42. 

 Gryphcea convexa, Morton (1828), Jour. Acad. Nat. Sci. Philad., VI, pi. 4, figs. 1 and 2 ; and pi. 5, figs. 1, 2, 



and 3; also (1834), Org. Rem., 53, pi. 4, figs. 1 and 2. 

 (irypha-u mntabilifi, Morton (1828), Jour. Acad. Nat. Sci. Philad., VI, pi. 4, tig. 3 ; and (1834), Synop. Org. 



Rem., 53, pi. 4, fig. 3. 

 Pycnodonta vesieularis, Fischer de Waldh. (1835), Bull. Mosc, VIII, 118.— Conrad (1860), Jour. Acad. Nat. 



Sci. Philad.. IV, 275. 

 Gryphcea vesieularis, Bronn (1848), Index Palaeout., 557 ; and of many other authors. 



Shell irregularly subhemispherical, or more or less variable in form, 

 rather thin ; anal side extended into a lobe. Under valve very gibbous ; beak 

 short, usually much distorted or truncated by the scar of attachment, moder- 

 ately curved upward, and sometimes not very distinct from the cardinal 

 margin ; ligament-area short, being modified by the distortion of the beak. 

 Upper valve flat or a little concave, and beveled within to the thin margins, 

 thickened somewhat toward the beak, which is truncated, and sometimes 

 slightly raised ; area small, transversely triangular, and standing nearly 

 vertical to the plane of the valve; lateral margins near the beak regularly 

 crenate. " Muscular impressions of both valves rather deep, and placed near 

 the middle of the left, or posterior, margin. Surface of lower valve nearly 

 smooth, or only showing obscure marks of growth ; upper valve with the 

 same kind of obscure concentric markings, and sometimes showing faint 

 traces of radiating striae. 



Length from beak to opposite margin, about 2 inches ; transverse diam- 

 eter, 2.33 inches; convexity of under valve, about 0.94 inch. 



It is not without some doubts and hesitation that I refer this shell to 

 G. vesieularis ; but after several careful comparisons, it has been found to 

 come so near forms which have been regarded by high European authorities 

 ;is only varieties of that variable species, that I have concluded that it will be 

 better to refer it doubtfully to the same, than to run the risk of adding 

 another synonym In a species that has already received such a multitude of 



