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SUPPLEMENT TO THE BRITISH 



Finding that the name mutabilis had been already made use of by Dr. Oppel 

 for another species in his paper on the " Unter-Lias von Hierlatz " (13th vol. of the 

 'Deutschen Geolog. Gesellschaft,' p. 538, 1861), Mr. Walker wishes to alter the name 

 he formerly gave to this species to that of Wanldyni, after Mr. A. Wanklyn, 

 Eellow of Sidney College, Cambridge, who has devoted much attention to the micro- 

 scopical condition of the shell of many of the species that occur at Upware. 



66. Waldheimia Woodwardi, Walker. Sup., PI. VI, figs. 1 — 5«. 



Waldheimia Woodwardi, Walker. Geol. Mag., vol. iv, p. 455, pi. xix, fig. 3, 1867; 



and vol. v, p. 404, 1S68. 



Spec. C/iar. Shell elongated, oval ; ventral valve very convex, strongly keeled, 

 lateral portion of the valve flat or slightly concave, much arched and incurved at the beak. 

 Beak short, and truncated by a moderate-sized foramen lying close to the umbo and 

 partly margined by two small deltidial plates ; beak -ridges sharply defined. Dorsal 

 valve more or less deeply depressed or concave, and slightly channelled along the centre ; 

 convex laterally and at the umbo. Margin curved, especially in front; Surface 

 smooth, marked by a few fine concentric lines of growth. Loop extending nearly to 

 the frontal margin. 



Length 21, width 12, depth 10 lines. 



Obs. This fine species was discovered and well described by Mr. Walker in 1867. 

 In his paper on the deposit at Upware (Geol. Mag. vol. iv, p. 310) he had referred it 

 to T. hippopus, Roemer, but subsequently found that it differed from Roemer's species 

 as well as from other known Cretaceous forms, and therefore named it after the late 

 Dr. S. P. Woodward. It approaches nearest to some specimens of W. carinata, Lam. ; 

 and many young specimens can scarcely be distinguished from the Jurassic W. impressa. 

 Mr. Walker states that it cannot be confounded with W. celtica on account of the shape 

 of its dorsal valve. Internal casts are occasionally met with, and present a singular 

 appearance (fig. 5). In the cast of the dorsal valve there exists a median fissure, which 

 extends to about one third of the length of the valve, and thus indicates the presence of 

 a small median septum. On either side are the muscular impressions, likewise margined 

 by a deepish groove. In some specimens the greatest breadth is in the anterior portion 

 of the shell, while in others it is the reverse. 



Position and Locality. — This species is not abundant in the Lower Greensand at 

 Upware. Very fine specimens may be seen in the Woodwardian Museum, Cambridge, 

 and in the collection of Mr. Walker, who, moreover, has deposited in the British Museum 

 a series of all the typical specimens described by him from Upware. Mr. Meyer informs 

 me that he has picked up some fragments of this species at Godalming. 



