140 MOLLUSCA FROM THE GREAT OOLITE. 



tumidd, lunuld magnd, excavatd; postice compressd, margins cardinali curvato, oblique 

 declivi; plicis incrementi magnis, paucis, irregularibus. Superficie granulis dense, ornatis> 

 granulis in lineis radiantibus minutis serialibus regularibus instinctis. 



Shell ovately cordiforra, the test very thin, anterior side very convex and produced 

 posterior side attenuated and compressed ; umbones depressed, placed at about one third 

 from the anterior margin, lunule large, excavated ; hinge border curved and sloping 

 obliquely downwards, its posterior extremity rounded. The sides of the valves have large 

 irregular but distant plications. 



The entire surface is very densely ornamented with minute granules disposed in closely- 

 arranged fine radiating lines, the lines being distinctly raised and uniting the granules 

 at their bases. 



Agassiz has not noticed the Unio pereyrinus, but his tab. XIV contains numerous and 

 truthful exemplifications of its phases of aspect under the names of Gresslya erycina and 

 G. concentrica. 



The most prominent distinguishing feature of Gresslya per egrina, consists in the great 

 development of the anterior side, and the compression of the posterior, so that when placed 

 upon its side, the anterior border and lunule faces the spectator. 



Some specimens of Gresslya latirostris, Ag., from the Inferior Oolite of the Cotteswolds, 

 much resemble our species in their general outline, but the more considerable diameter 

 through the valves upon the anterior side of G.peregrina, will always distinguish it, together 

 with the more compressed and shortened figure of the posterior side. 



From Gresslya abducta (Unio abductus, Phil.), it is readily distinguished by the more 

 elevated umbones and shorter anterior side of the latter species. 



Geological position and localities. Gresslya peregrina occurs both in the Cornbrash, 

 and in the Grey Limestone of the Great Oolite, near Scarborough. 



GONIOMYA V-SCRIPTA, Sow. Sp. Tab. XIII, fig. 16. 



Syn. MYA V-SCRIPTA, Sow. Min. Con., t. 224, f. 2 5. 



GONIOMYA V-SCRIPTA, Ag. Etud. Crit. Myes., t. 15, f. 17 19. 

 GONIOMYA V-SCRIPTA, Morris. Catnl. 2d edit., 1854, p. 203. 



Testa ovato-subtrigond, umbonibus submedianis, margine antico rotunda, postico sub 

 truncato, costis angulis acutis verticalibus, extremitate postico lavi. 



Shell ovate, somewhat subtrigonal ; umbones nearly mesial ; anterior border rounded ; 

 posterior border somewhat truncated, lower margin nearly straight ; from the umbones the 

 anterior and posterior margins slope obliquely downwards, the posterior side, which is 

 slightly the longer, having its slope at a smaller angle than the other ; costae numerous, 

 their angle acute, and directly perpendicularly downwards, or a little backwards ; the 



