38 MOLLUSCA FROM THE GREAT OOLITE. 



half the length of the shell, and is greater than the height ; the general form is therefore 

 narrow, very convex, and curved elliptically. 



It occurs very rarely in the shelly beds of the Great Oolite. 



Locality. Minchinhampton Common. 



MTTILTJS PTJLCHERRIMUS, Roemer, var. Tab. IV, fig. 12, 12 a. 



MODIOLA PDLCHEERIMA, Roemer. Verst., p. 34, t. 4, f. 14, 1836. 



Koch and DunJcer. Beitr. Oolith., t. 6, f. 7, 1837. 

 MTTILTJS PTJLCHERKIMUS, Goldfuss. Petref., p. 177, t. 131, f. 9. 



Testa ovato-fornicatd, umbonibus postmedianis return, margine cardinali recto, later e 

 inferiore convexo, postice sudretuso, lineis radiantibus crebris superne crassioribus con- 

 eentricis decussatis. 



Shell ovate, with an elevated dorsal ridge, umbones postmesial, extended backwards, 

 hinge margin straight, inferior side convex, with radiating lines closely arranged upon the 

 superior side, and decussated by very fine concentric lines, which form knots where they 

 cross the longitudinal elevations. 



The general figure is subquadrate, the height being equal to hah the length, and the 

 diameter through both valves is a little less than the height ; the usual length is about 

 four lines ; the test is delicate and fragile. 



Localities. All our specimens have been obtained in the bed of the soft Shelly Oolite, 

 which at Minchinhampton Common underlies the planking. It is moderately rare. 

 Ancliff, Wiltshire, (Mr. J. D. C. Sowerby's Collection.) 



MYTILUS SOLENOIDES. Tab. IV, fig. 4. 



Testa prcelongd, ettipticd, concentrice rugoso striatd, antice vix angustatd, obtusd, 

 postice paulum depressd et dilatatd ; margine cardinali subrecto, margine inferiore in 

 media subsinuato. 



Shell elongated, elliptical, gibbose, with rugose concentric striae, anterior extremity 

 rather narrow and obtuse, posterior extremity more depressed and dilated, hinge margin 

 nearly straight, inferior margin sinuated. 



The general aspect has a considerable resemblance to Mytilus plicatus, but it is much 

 more gibbose, the diameter through both the valves being upwards of one third of the 

 length, and it is destitute of the posterior plicae, which distinguish that species; the con- 

 centric striae are very prominent and irregular. 



Modiola elongata, Koch and Dunker, which is probably Modiola scalprum, Sowerby, 

 is also less gibbose. 



Locality. The Slaty Oolite of Minchinhampton Common, rare. 



