BIVALVIA. 253 



Shell ovately oblong, rounded at both extremities, slightly inequilateral, compressed 

 in the middle, with a small contraction in the ventral margin ; one half covered with 

 oblique striee. 



Length, 2 inches. 



Locality. Cor. Crag, Sutton. Recent, Britain? Mediterranean. 



My specimens are few and fragmentary. They appear to possess about twenty-two 

 divergingly imbricated ridges, or lines, covering about two thirds of the shell. These 

 lines are vertical in the centre, one or two sloping a little towards the anterior. 



There are the remains of colour in my specimens, and they correspond in that respect 

 with what the British conchologists consider to be distinct, and different from the white 

 variety, which is ornamented with the same kind of sculpture. The lines on my 

 fossil do not appear to extend quite so far upon the anterior side as in the recent shells, 

 but there is little doubt of its identity with either this or M. Candida. Philippi gives 

 both as inhabitants of the Mediterranean, as well as fossil in that part of the world, 

 distinguishing the two species in the fossil state by the number of rays. This, I am 

 afraid, is a questionable distinction ; specimens of the red variety may be observed, on 

 which may be counted the same number he has given to each species. 



In that extraordinary book, Pontoppidon's 'Nat. Hist, of Norway,' p. 165, there is 

 the figure of a shell called the smaller mussel, which is one of the varieties of this 

 species, but it is not enumerated by Loven in his ' Ind. Moll. Scand.' The shell from 

 the Older Tertiaries, Solen strigillatus, Lamarck, 'Ann. du Mus.' t. 12, pi. 43, fig. 5, is 

 distinct ; the one referred to by Basterot (p. 96), from the neighbourhood of Bordeaux, 

 I have not seen. 



Solen,* Arist., Linn,, 8fc. 



Solena. Broivne, 1756. 



Hypog^ea and Hypogeoderma (sp.) Poll, 1/91. 



Solenarius? Bumeril, 1806. 



Vagina. Megerle, 1811. 



Ensis. Schum, 1817. J. Sow. 1846. Gray, 1851. 



Ensatella. Swains. 1840. 



Generic Character. Shell equivalved, transverse, linear, subcylindrical, straight or 

 very slightly curved, gaping widely at both extremities, dorsal and ventral margins 

 nearly parallel, umbones near the extremity. Hinge with two teeth in one valve, and 

 one in the other, with sometimes a linear lateral tooth. Muscular impressions dis- 

 similar. Palleal sinus short and wide. Ligament external, attached to an elongated 

 fulcrum. In the recent state, covered with a thick epidermis. 



* Etym. (twXjjv, a tube. 



