54 RAMBLES IN SEARCH OF SHELLS. 



Assiminia gray ana differs from Hydrobia in not 

 having the eyes placed on tubercles, and from the 

 marine Rissoa in the tentacles being united to the 

 eye-stalks, which equal them in length. The shell, 

 of a liver-brown colour, is ovate-acute, with five 

 whorls, and about a quarter of an inch in length. 

 The suture is slightly impressed ; there is no um- 

 bilicus ; the aperture is ovate ; the operculum horny, 

 ovate, and of a blackish-brown colour. It inhabits 

 the banks of the Thames between Greenwich and 

 Gravesend, and is tolerably abundant, living on the 

 mud beneath the shade afforded by Scirpus mari- 

 timus and Festuca arundinacea.* 



* "The nnmber of estuarine species," says Mr. Tate, " which 

 have a place in our works devoted to British land and fresh- 

 water snails is very few, and the majority, moreover, are 

 confined to the margins of the tidal rivers in the South of 

 England. Thus Assiminia grayana, HydroMa ventrosa, 

 and' H. similis, live on the mud-banks beneath the shade of 

 sedges and rushes, skirting the Thames below Greenwich. 

 To gather these small shells singly is a tedious operation ; 

 but if a thin piece of flat wood, or other substitute as the 

 ingenuity of the collector suggests, be used to scrape lightly 

 over the surface of mud, transferring the mass to the dredger, 

 or tin sieve and washing in water, a number of specimens, 

 sufficient to stock every private cabinet in the country, may 

 be obtained in a short space of time." 



