BIVALVIA. 1 1 1 



Spec. Char. N. testa, elongato-ovatd, turgidd, tumidd, inaquilaterali ; laevigata, glabra, 

 margin e dorsali subrectd, pedi-regione ovatd ; siphoni-regione, prcelongd, subrostratd; mar- 

 gine ventrali convexd; lunula vix conspicud ; apicibus depressis ; marginibus integris. 



Shell elongately ovate, inflated, inequilateral, smooth and glossy ; dorsal margin 

 nearly straight ; ventral margin convex ; pedal region large, ovate ; siphonal region 

 obtusely pointed ; lunule inconspicuous ; beaks depressed ; margins smooth. 



Length, T 9 B ths of an inch ; height, ^ths of an inch. 



Localitg. Hampstead Heath {Wetherell) ; Potter's Bar, and Highgate {Edwards). 



The peculiar distinction is the pointed or subrostrated form of the siphonal region, 

 where it is slightly compressed, from which I presume it received its name, as the shell is 

 otherwise rather tumid. 



6. Nucula consors, S. Wood. Tab. XIX, fig. 7, a, b. 



Ncctjla similis. J. Sow. Min. Conch., vol. ii, p. 20", t. 192, figs. 3, 4, 1819. 



Spec. Char. N. testa obovatd, transversa, subtrigonuld, turgidd, valde inaquilaterali, 

 obsolete radiatd, aliquantisper striis transversis decussatd ; pedi-regione prolongd, obtusd ; 

 siphoni-regione rotundate truncatdj margine ventrali convexd ; lunula vix distinctd ; ano 

 ovato in medio prominenti ; marginibus crenulatis. 



Shell transverse, obtusely ovate, roundedly trigonal, turgid, very inequilateral, obsoletely 

 rayed, slightly decussated by lines of growth ; pedilateral margin obtusely or roundedly 

 angulated ; dorsal and ventral margins convex ; lunule indistinct ; anal region slightly 

 prominent ; internal margins crenulated. 



Length, \ an inch ; height, |ths of an inch. 



Localitg. Highgate {Wether ell). 



Many specimens of this species are in the cabinet of Mr. Wetherell ; but they are 

 seldom in good condition, the greater number of them being merely casts. 



Professor Morris, in his ' Catalogue of British Possils,' has rejected figs. 3 and 4, 

 t. 192, 'Min. Conch.,' from being identical with the Barton species figured upon the same 

 plate, and Mr. Sowerby says, at p. 208, he is doubtful whether fig. 4 ought not to be 

 considered a distinct species, or at least a distinct variety, implying thereby a doubt as to 

 the propriety of admitting it under the name of similis. I have, therefore, given it a new 

 specific name with more confidence, having the support of the above two opinions. It 

 resembles in many of its characters one or two species from the Middle Eocene, but with 

 none does it appear to be truly identical. It has no distinctly marked lunule. There is 

 a prominent anal region surrounded by a depression, and in those specimens which are 

 best preserved the radiating stria? are very distinct, decussated by lines of growth. The 

 two valves are most commonly united, and many of them have been perforated by a 

 zoophagous feeder. 



