148 



CONCHIFERA. 



Gryph^a. 



undulations diverge from the central furrow ; margins slightly 

 foliated. 



Great Oolite, Western Yorkshire. 



37. OsTBEA INDISTINCTA. — The Indistinct Ostrea, pi. 

 LVIII. fig. 8. 



Ostrea ? Geo. York, I. p. 109 and 180, pi. 5, fig. 12. 

 Oblong, obliquely triangular, surface smooth. 

 The Oxford Clay, Scarborough. 



38. Ostrea triangularis. — The Triangular Ostrea, pi. 

 LXL* figs. 9, 10. 



0. triangularis. "Woodward, pi. VI. fig. C, 7. 

 Triangular, oblong, oblique, with acute beaks ; surface rather 

 smooth. 



In the Chalk, Norfolkshire. 



Genus XVIII.— GRYPH^A.—Zawarc^. 



Shell free, inequivalve, upper valve small, flat, and acting 

 apparently as a lid to the under one, which is large, concave, 

 and arcuated, with an incurved prominent umbo ; hinge des- 

 titute of teeth, with a curved depressed area ; provided in- 

 teriorly with one muscular impression in each valve. 



1. Gryph^a incurva. — The Incurved Gryphsea, pi. LX. 

 fig. 1. 



Gryphcea incurva. Sowerby, II. p. 23, pi. 112, figs. 1, 2. 

 Parkinson, p. III. 209, pi. 15, fig. 3. Goklfuss, pi. 84, fig. 1. 



Elongated ; larger valve greatly incurved, the point of the 

 beak frequently concealed ; when visible, it is usually sharp, 

 seldom exhibiting any impression ; lesser valve a little ob- 

 long, in the form of a lid, narrow towards the inner side, and 

 gradually widening outwards, and externally concave ; surface 

 considerably undulated concentrically ; sometimes laminated ; 

 sides straight, gradually widening towards the rounded front. 



The Lias, of which it is a highly characteristic fossil, in 

 England, Germany, and France. 



2. Gryph^a bullata. — The Gem Gryphsea, pi. LX. 

 fig. 2. 



Gryphwa bullata. Sowerby, IV. p. 93, pi. 368. Phillips, 

 Geo. York, I. p. 4, fig. 36. 



Transversely obovate, irregular, thin, smooth, and com- 

 pressed ; upper valve considerably less than the other, which 

 is undulated, concave, with concentric irregular lines of growth ; 

 beaks very small, that of the lower valve much incurved ; lateral 

 lobe small and obscure ; point of attachment very small. 



Kimmeridge Clay, Bedford and Norfolk, the Middle 

 Oolite, Wiltshire and Yorkshire. 



3. Gkyph^a Macullochii. — Maculloch's Gryphsea, pi. 

 LX. fig. 19. 



Gryphwa] Macullochii. Sowerby, VI. p. 89, pi. 547. 

 Goidfuss, pi. 64, fig. 4. 



Longitudinal, obovate, gibbose, and oblique ; beaks much 

 produced and incurved ; base rather angular ; posterior lobe 

 more or less distinct ; surface strong, with curved lines of 

 growth. 



This fossil is intermediate between G. incurva and G. dila- 

 lata, but is much shorter than tlie latter and greatly thicker. 



Lias, at Pabba and Scalpa, Hebrides, and Robin Hood's 

 Bay. 



4. Gryphsea Columba. — The Pigeon Gryphsea. pi. LXI. 

 fig. 15. 



G. Columba. Sowerby, IV. p. 113, pi. 383, figs. 1 and 2. 

 Exogyra Columba. Goidfuss, pi. 86, fig. 9. 



Ovate ; rounded ; beak nearly central, much attenuated ; 

 incurved obliquely ; posteriorly expanded ; surface smooth ; 

 upper valve slightly striated near the hinge, and more or 

 less quadrangular ; largely undulated ; its posterior margin 

 thick and flattened ; opposite valve obtusely carinated. 



Greensand, Lyme and Devonshire. 



5. Gryphwa depressa. — The Depressed Gryphsea, pi. 

 LXI. figs. 19. 



G. depressa. Phillips, I. p. 134, pi. 14, fig. 7. 



Ovate, oblique ; beaks obtuse, turned to one side ; margins 

 and surface smooth, with distinct lines of growth ; flat valve 

 nearly plain. 



Lias, Bilsdale, Yorkshire. 



6. Gryphwa dilatata. — The Extended Gryphcea, pi. 

 LXI, fig. 1, 6, 7. 



G. dilatata. Sowerby, II. p. 113, pi. 149, figs. 1, 2, variety 

 Phillips, I. p. 112.pl. 6, fig. I. 



Orbicular, obscurely lobed, upper valve compressed, quite 

 flat, with an obtuse umbo ; under valve hemispherical, with 

 its umbo rather large and incurved, remote from that of the 

 other valve. 



The variety, fig. I. has a distinct lobe, and longitudinal furrow on the 

 narrow side of the deeper valve. 



Portland Sand, Langcomb, Oxon; Kimmeridge Clay, Bed- 

 ford ; Kelloways Rock ; Scarborough and Hackness, and the 

 inferior Oolite, near Cheltenham. 



7. Gryphwa gigantea. — The Gigantic Gryphaea, pi. 

 LXI. fig. 5. 



Gryphcea gigantea. Sowerby, IV. p. 127, pi. 391. Gold- 

 fuss, pi. 85, fig 5. 



Nearly orbicular; upper valve thin and concave; lower 

 valve convex, with a small, sharp, incurved umbo ; hinge 

 small ; surface rather smooth, with imbricated laminae, which 

 in the lesser valve are but slightly developed, even, and situate 

 at regular intervals ; anterior lobe separated by a small sinus 

 in the edge of the laminjc ; depth about a fifth of its length. 



It is probable that G. bullata and dilatata are only varieties of this 

 species. 



Great Oolite, White Nab ; Inferior Oolite, Ilminster and 

 Lias, Prees. 



8. GryphjEA globosa — The Globular Gryphsea, pi. LXI. 

 fig. 2. 



G. globosa. Sowerby, IV. p. 127, pi. 392. Ostrea fassicu- 

 laris, Brongniart, Env. de Paris, pi. 3, fig. 5. 



Obliquely subglobose, thin and smooth ; beak much trun- 

 sated ; upper valve concave ; hinge-line straight ; anterior 

 lobe very conspicuous ; a small additional muscular impres- 

 sion situate near the hinge. 



Upper Chalk, Gravesend and Sussex ; and the Red Chalk 

 Hunstanton. 



9. Gryphwa nana. — The Dwarf Gryphtea, pi. LXI. figs. 

 3,4. 



G. nana. Sowerby, IV. p. 114, pi. 383, fig. 3. 

 Oblong-ovate, inflated ; surface rugged ; umbo pointed, 

 obliquely incurved ; upper valve acute and thick ; variable in 



