190 coiiBULiDii':. 



posed of an erect dilated laminar tooth in one valve, with a 

 corresponding pit in the other. Ligament internal. Pallial 

 impression with a slight sinuation. 



Animal ovate ; mantle closed in front, except an opening 

 for the passage of a small digitiform foot, furnished with a 

 byssal groove. Siphons united to their extremities ; their 

 orifices cirrhated. Anal siphon with a tubular membranous 

 valve projecting beyond the orifice. 



This rare and curious genus is as yet but very im- 

 perfectly known, and, thanks to the observations of Mr. 

 Clark, we are enabled now, for the first time, to give some 

 account of its animal. In his manuscripts he offers the fol- 

 lowing remarks with respect to its systematic position : — 

 " Though not far removed from Mya and Saxicava, the 

 animal is perfectly distinct, and so similar to Corhula, that 

 it is difficult to point out more than a specific difference. 

 Dr. Turton is perfectly right (though, we presume, by 

 chance) in placing this species of SphtEuia next to Corbula." 



The shell has evidently, at a glance, a striking resem- 

 blance to the Saxlcava, and may be passed over as such ; 

 but the notes of Mr. Clark on the animal remove it to 

 another family. In some respects it has considerable affi- 

 nity with certain exotic forms of the genus Lyonsia, and 

 thus aids in maintaining the passage evident in several 

 of the Corbulida from the gapers and borers to Thracia 

 and its allies. 



S. BiNGHAMi, Turton. 



S2)hcettia Binf/Jiami, Turt. Dithyra Brit. p. 36, pi. 3, f. 3, 4, 5.— Flem, Brit. 

 Anim. p. 4C5.— Brit. Marine Conch, p. 57, f. 32, 33.— 

 Brown, Illust. Conch. G. B. p. 104, pi. 42, f. 17, 18, 22. 

 — SowEiiBv, Conch. Manual, f. 06. 



Corbula „ H.VNL. Recent Shells, p. 47, suppl. pi. 12, f. 4. 



