136 LITTORINID.E. 



rounded anteriorly, and, owing to the lateral projection of 

 the outer lip above, is not acutely peaked posteriorly. 

 The peristome is continuous, but the parietal enamel is but 

 thinly sj^read ; the throat is quite smooth. The acute 

 and simple outer lip has no tendency to expand ; it is 

 arched below, but merely convex above. The pillar-lip, 

 which is not appressed, is long, narrow, and reflected ; 

 behind it exists a distinct umbilicus. Specimens in general 

 measure two lines in length, and from a line and a quarter, 

 to a line and a third in breadth. 



The animal is of a grey colour marked with dark brown. 

 Its head is rather large, with a very prominent and rather 

 broad muzzle, which as well as the crown of the head and 

 neck is of a dark dusky brown colour. The tentacles are 

 long and setaceous, yellowish white, or pale grey, with a 

 fine brown line down their centres above. Their bases are 

 of an opaque pale yellow, and bear on the outsides of 

 their bulgings, large, prominent black eyes. The sides 

 are dusky grey, lineated more or less with brown. 

 The foot is very broad, square, and obtusely angled in 

 front, rounded behind, expanded and depressed, its caudal 

 extremity not bearing a filament, and extending con- 

 siderably beyond the ovate, short spired, simply corneous 

 operculum. The denticles of the tongue are arranged, 

 and resemble in form those of the typical Missoa, so as 

 to place the generic affinities of this species beyond ques- 

 tion, and to prove that it is not a Littorina, as some 

 malacologists have considered it. Together with the two 

 succeeding species, like its inhabitants of brackish Avater, 

 it may be considered as constituting what Milne-Edwards 

 would aptly term, a " satellite " group to the genus 

 Rissoa. The names Hydrohia (Hartmann), Paludesfrina 

 (Alcide d'Orbigny), Paludinella (Loven, but not PfeifFer), 



