64 



founded by Hartmann in 1821. An objection has been 

 made to the name on the ground that it had been pre- 

 viously used for a genus of small water-beetles ; but it 

 does not seem that any confusion or inconvenience is 

 likely to result from the use of the same name in such 

 different departments of zoology, and precedents are not 

 wanting for such a double application. We have only 

 two species of Hydrobia ; but on the Continent there 

 are four or five times that number, including Hydrobia 

 marginata which existed during the Glacial epoch in our 

 eastern counties and Bedfordshire, but appears not to 

 have survived that period. 



The estuarine or brackish-water species of Hydrobia 

 were formed by Professor D'Orbigny into another genus, 

 which he called Paludestrina ; and these also constitute 

 the genus Paludinella of Pfeiffer and Love*n. 



1. HYDROBIA SI'MILIS*, Draparnaud. 



Cydostoma simile, Drap. Moll. Terr, et Fluv. Fr. p. 34, pi. i. f. 15. 

 JRissoa anatina, F. & H. iii. p. 134, pi. Ixxxvii. f. 3, 4. 



BODY dark grey, with a yellow or brown tint and white 

 flaky specks : head rather large and prominent : snout broad, 

 long, and ridged transversely : tentacles long, slender, and 

 diverging : eyes large and rather protuberant -.foot short, very 

 broad, and expanded on each side in front, rounded behind, 

 and extending considerably beyond the operculum when the 

 animal is crawling. 



SHELL subconical or oval, rather thin, glossy, semitrans- 

 parent, yellowish horn-colour, or sometimes clear- white, ob- 

 scurely and slightly marked by the lines of growth : epidermis 

 a mere film : whorls 5-6, rounded, but compressed ; the last 

 exceeding one-half of the shell : spire rather pointed : suture 

 somewhat oblique and deep, forming a narrow canal : mouth 

 oval : outer lip thin, slightly reflected : inner lip united to the 

 columella, but continuous with the outer lip : umbilical chink 

 oblique, small, but distinct : operculum oval, obtusely angular 



* Resembling another species, 



