BIVALVIA. 39 



MYTILUB SOLENOIDES, var. SUBRENIFORMIS. Tab. IV, fig. 11. 



Testa crassd subdepressd aut subreniformi, lavigatd, umbonibus obliquis terminalibus, 

 margine superiore arcuato, margine inferiore excavato aut subsinuato, plicis incrementi 

 paucis irregular ibus. 



Shell thick, rather depressed, or kidney-shaped, smooth, umbones oblique, depressed, 

 terminal, superior margin curved, inferior margin excavated or somewhat sinuated, folds of 

 growth few and irregular. 



The two extremities of the shell are nearly equally rounded and convex, an obscure 

 and obtuse dorsal ridge extends in a curved direction from the umbones to the posterior 

 and inferior extremity; the superior side of the shell has a considerable convexity, and the 

 inferior or ventral side is compressed. 



We have only obtained two specimens of this species, which occurred in the soft 

 shelly Oolite which underlies the planking. 



Height, 6 lines ; length, 14 lines ; diameter, through both the valves, 6 lines. 



Locality. Minchinhampton Common. 



MYTILUS FURCATUS, Goldf., var. BATHONICOS, nob. Tab. IV, fig. 9, 9 a. 



MYTILCS FURCATUS, Goldfuss. Petref., t. 129, f. 6. 



Roemer. Nordd. Ool., p. 33, t. 18, f. 38. 

 ?MODIOLA ASPEKA, Phillips. Geol. York., t. 11, f. 9. 



Testa ovato-acutd, injlatd, umbonibus acutis, margine cardinali subrecto obliquo, latere 

 inferiore abrupto, costis crebris subpapittosis interdum dichotomis, lineis incrementi paucis 

 magnis irregularibus. 



Shell ovately acute, very convex, with terminal acute umbones ; hinge border straight, 

 or rather oblique, anterior border steep and excavated ; costae numerous, closely arranged 

 and indented with concentric striations, producing a papillary surface, the costse are waved 

 and occasionally dichotomous. The specimens rarely show the imbricated costae. 



The larger and indented costse distinguish it from M. asper, Sow. It is not 

 uncommon in the shelly beds of the Great Oolite, and varies in length from 3 to 16 lines. 



Locality. Minchinhampton Common. 



MYTILUS ASPER, Som. Tab. IV, fig. 8. 



MODIOLA ASPEUA, Sow. Min. Con., t. 212, f. 3, 1818. 



Testa cuneatd gibbosd, arcuatd longitudinaliter striatd, lineis numerosis radiantibus 

 furcatis, imbricatis ; umbonibus incurvis subacutis, margine cardinali arcuato, posterior^ 

 subrecto. 



An elongated arched gibbose and longitudinally striated shell, with rather small and 

 curved beaks ; striae numerous, furcate, and minutely imbricated. 



