138 MOLLUSCA FROM THE GREAT OOLITE. 



Locality. Myacites decurtatus occurs in the Cornbrash both of Yorkshire and of 

 Wiltshire; we have also been favoured by Mr. Bean, with a specimen from the Great 

 Oolite near Scarborough. 



Myacites scarburgensis, Phil. Sp. Tab. XV, fig. 13. 



Syn. Lutrakia gibbosa, Phil. Geol. York., 1, t. 9, f. 6. 



Testa, ovato-elo?igatd, compressiusculd, umbonibus antemedianis parvis, margins antico 

 rotundo, producto, postico elongato, hiante; basi elliptico curvato, margine superiori sub- 

 horizontali, concavo; lateribus compressis, plicis irregularibus inagnis longitudinalibus. 



Shell ovately elongated, compressed ; umbones anterior to the middle of the valves, 

 small and not much elevated ; anterior side produced, its margin rounded ; posterior side ' 

 lengthened, and gaping with a moderately large aperture ; base curved elliptically ; the 

 sides of the valves are compressed, and have large irregular longitudinal plications ; the 

 ligamental area is large and excavated, the posterior aperture extending upon the horizontal 

 superior border nearly to the ligament. 



A species somewhat resembling Myopsis Jurassi, Ag., but less tumid, or more com- 

 pressed in its middle part. 



Height, 17 lines; length, 31 lines; diameter through both the valves, 12 lines. The 

 specimen figured is the original one drawn by Professor Phillips. 

 Locality. Scarborough. Mr. Bean's Collection. 



Myacites gibbosus, Sow. Sp. Tab. XII, fig. 14, (junior.) 



Syn. Panop^a gibbosa, Sow. Min. Con., t. 211. 



— Agassizii, Valenc. Arch, du Mus., 1, p. 31. 

 Myacites gibbosus. Morris. Catal. 2d edit., 1854, p. 213. 

 Mya gibbosa, IfArchiac. Mem. Soc. Geol. Fr., vol. 5, pi. 26, f. 1, 1845. 

 — modica, Bean. MSS. (junior.) 



Testa ovato- oblong a, ventricosd, umbonibus rotundis, magnis, elevatis ante medianis, 

 latere antico brevi, margine rotundo, latere postico compresso, margine aperturd angustd, basi 

 elliptico curvato ; margine superiori concavo ; area ligamenti magna, ellipticd ; lateribus 

 striis irregularibus tenuissimis. 



Shell ovately oblong, ventricose ; umbones rounded, large, elevated, and placed anterior 

 to the middle of the valves ; anterior side short, convex ; its margin rounded, gaping with 

 a small aperture ; posterior side compressed, its extremity with a narrow lengthened 

 aperture ; base elliptically curved ; superior margin rather concave ; ligamental area large, 

 elliptical, depressed ; sides of the valves with fine irregular longitudinal striations. 



The small specimen forwarded us from the Great Oolite of Scarborough, is the young 



