370 Mr W. Macgillivray on Anatina Villosiuscula. 



diately replenished with it. By this day's observation we were 

 125 miles from Chittagong, and about 100 from the nearest part 

 of the Junderbunds. The water was of a more yellow tinge 

 than in most parts of the bay ; and those who drank a great 

 deal of it, suffered from it afterwards. 



Description of Anatina villosiuscula^ a new Species, and of 

 Venerupis Nucleus, a Species new to the British Fauna. 

 By Mr William Macgillivray, M. W. S., &c. With 

 Figures. Communicated by the Author. 



I. Anatina villosiuscula. PI. I. fig. 10, 11. 



Spec. Char. — J^, testa ovata ventricosa, inaequivalvi, antice 

 subtruncata, rugosa, minutissime granulata. 



Description. — Shell ovate, ventricose, inequivalve, with the 

 umbones nearer the anterior extremity, the posterior extremity 

 rounded, the anterior subtruncate, thin, fragile, diaphanous, 

 transversely wrinkled, white, slightly tinged with yellow. Right 

 valve larger, and much more convex, with a more prominent 

 umbo; umbones directly opposite; ligament double, the external 

 short. One transverse scarcely prominent tooth in each valve, 

 resembling an incrassation of the margin, immediately behind 

 which, and directly under the umbo, is a deep sulcus. Poste- 

 rior extremity shut close, anterior hiant. External surface co- 

 vered with very minute prominent points, which, to the naked 

 eye, are not individually distinguishable, but aggregatelv pro- 

 duce a dull or lustreless appearance ; internal surface smooth- 

 ish, shining at the ends, glimmering about the middle. 



It will be perceived that this shell is closely allied to A. mya- 

 lis of Lamarck, which is Mya puhescens of Turton, as well as to 

 several others, such as Anatina trimcata of Lamarck. It would 

 be tedious to enter into all the explanations necessary for the 

 accurate distinction of species so intimately connected. Our 

 British conchologists have sadly puzzled themselves with this 

 genus, which they have most injudiciously stuck to the genus 

 Mya, after Linnaeus's example ; so that, to clear up all diffi- 

 culties, would require a monograph. 



