BIVALVIA. 115 



sertion to as many corneous prickles ; but we have not been able to trace this feature in 

 all specimens. 



The species most nearly allied are Sanguinolari a ? rotunda, 'Geol. Chelt.,' pi. 0, 

 fig. 3, and Panopcea Guibaliana, Buvignier, 'Geol. de laMeuse,' Atlas, pi. 8, fig. 3 — 5, 

 but it is more trumpet-shaped and less elongated than the former, and less compressed 

 than the latter. 



Localities. Small excavations on the southern slope of Minchinhampton Common, 

 in the Great Oolite ; also in the Cotteswolds generally in the fullers' earth and Inferior 

 Oolite ; Glaizedale, Yorkshire. 



Myacites Terqtjemea, Buv. sp. Tab. XII, fig. 6. 



Syn. Plexjromya tenujstma, Ag., 18-18, pi. 24. 



Paxop^ea tenuistria, If Orb., 1850, Prod., 1, etag. 10, No. 242, (non Buv.) 

 Non Lutraria tenuistriata, Munst. in Gold/., pi. 153, fig. 2. 

 Panop.ea Terqtjemea, Buvig. Paleont. Dep. de la Meuse, Atlas, p. /. 



Testa obovatd, ventricosd ; umbonibus subacutis, antemedianis, latere antico cordato- 

 declivi, subdepresso, postice attenuato, aperturd parvd ; plicis longitudinalibus tenuibus. 



Shell obovate, ventricose mesially ; umbones rather acute, anterior to the middle of the 

 valves ; anterior side rather compressed, its border rounded ; posterior side attenuated, 

 its border slightly gaping ; lower margin curved ; longitudinal plications delicate. 



The greatest diameter through the valves is a little anterior to the umbones, which gives 

 a somewhat ventricose aspect to the figure. 



Length, 10 lines; height, 10 lines; diameter through both the valves, 8 lines. 



Geological position and localities. Our specimens are from the shelly beds of Minchin- 

 hampton Common, where it is very rare. Agassiz and Goldfuss have recorded it in the 

 lower Oolitic rocks of France and Germany. 



Myacites unioniformis. Tab. X, fig. 6. 



Testa tumidd, ovato-elongatd ; umbonibus magnis, subcompressis ; margine antico et 

 postico rotundo ; margine superiori concavo, lateribus lavigatis ; sulco lata superfciali ab 

 umbone ad marginem inferiorem producto. 



Shell tumid, ovately elongated; anterior side short; posterior side elongated; both 

 anterior and posterior margins rounded ; the posterior margin gapes but slightly; the hinge 

 margin is elongated and concave ; the area is lengthened, lanceolate, or narrow, and 

 distinctly marked ; the ventral margin is somewhat rounded ; a wide, superficial depression 

 extends from the umbo obliquely to the inferior border, and renders the anterior side 

 nearly as much compressed as the posterior ; the surface is smooth with faintly-marked 

 irregular concentric plications. 



