BIVALVIA. 119 



Tellimya suborbicularis. Brown. Illust. Conch. Gr. Brit., pi. 14, figs. 14, 15, 1827. 

 Tellimya lactea? Id. .... pi. 14, figs. 10, 11. 



— tenuis. Id. .... pi. 14, figs. 12, 13. 



— — Smith. Wern. Trans., vol. viii, p. 45, 1838. 

 Bornia inflata. Phil. En. Moll. Sic, vol. i, p. 14, and vol. ii, p. 11. 

 Erycina pisum. Scacchi. Catal., p. 6, figs. 1 and 2, 1836. 



Spec. Char. Testa tumidd, orbiculato-oblongd vel sub orbicularis subaquilaterali, tenui, 

 fragili ; striis tenuibus incrementi distinctis ; cardine bidentato, dentibus lateralibus 

 remotis. 



Shell tumid, roundedly-oblong or suborbicular, nearly equilateral, very thin and 

 fragile ; smooth or covered with very fine lines of growth ; hinge with two cardinal 

 teeth in one valve and one in the other, lateral teeth remote. 



Diameter, \ of an inch. 



Locality. Coralline Crag, Sutton. 

 Red Crag, Walton Naze. 



Recent, Britain, Scandinavia, and Mediterranean. 



The animal of this species, which may be considered the type of the genus, has 

 been examined by Mr. Alder, and a description published in his valuable Catalogue of 

 the ' Mollusca of the Coast of Northumberland' (page 94), where he has pointed out a 

 remarkable deviation from the normal form of the Bivalvia, which in general have the 

 siphonal tube or tubes, when they exist, placed at the posterior side of the shell, while in 

 this one, in addition to a short siphon in its natural position, there is a large tube capable 

 of being projected a considerable distance on the anterior side. The mantle has three 

 openings, he says, one posteriorly for the usual siphon which scarcely projects beyond 

 the margin of the shell ; another in front in the form of a tube, which is protruded when 

 the animal is in a state of activity, to a distance equalling the diameter of the shell; and 

 the third is for the emission of a long subcylindrically-formed foot, at the base of which 

 is a small opening and gland for the production of delicate threads or filaments, whereby 

 the animal is enabled freely to suspend itself in the water to some foreign body 

 although it is more often found located in the aperture of a rock. 



A considerable degree of variation in form may be observed among the shells of 

 this species in the recent state, but it is more particularly so with those which are 

 found in the crevices of rocks, which probably in some measure distort or alter the 

 otherwise natural form of the shell. This species is not by any means common in the 

 Coralline Crag. 



The more general form of my fossils is nearly orbicular, but one specimen (fig. 8, b) 

 is more transverse, or has a greater diameter from the anterior to the posterior 

 extremity : the same differences exist in those now found in our own seas. The Red 

 Crag at Walton Naze has furnished me with one specimen. It is said to range from 

 low-water mark to a depth of 60 fathoms. 



