2 28 NOTES ON THE MOI.LUSCA OF THE THAMES ESTUARY, 



{Acha/ina) acicula attached to it. This confirms my idea that this 

 latter species certainly does exist, either upon the marshes or in their 

 immediate neighbourhood, although from its burrowing habits it has 

 hitherto been overlooked.^ 



[It may be useful to append the titles of some papers on Hydrohia and allied 

 forms of Mollusca of our Essex marshes, which have recently appeared : — 



J. T. Marshall. " On Hydrobiae and Assimineoe from the Thames Valley." — 



" Journ. Conchology," vi. (1889), pp. 140-142. 

 Ibid. " Further Notes on the British Hydrobiae," l.c , pp. 224-225. 

 E. A. Smith. " Notes on British Hydrobiae, with description of a supposed 



new species," I.e., pp. 142-145. 

 Ibid. " A reply to Mr. J.T. Marshall's ' Further Notes on British Hydrobioe,'" 



I.e., pp. 244-246. 

 Ibid. " Note on HydrobicF jenkinsi." — " Essex Nat.," vol. iv., pp. 212-213. 

 A. J. Jenkins. "Distribution and Habits of the British Hydrobioe." — 



" Science Gossip," 1890, pp. 103-106. 

 //;/(/. " Note on H.jenkensi." — "Science Gossip," i8gi, pp. 184-185. 

 A. J. Jenkins and L. 0. Groeoek. " Notes cjncerning the Distribution of 



Mollusca in the Thames Estuary," I.e., 1891, pp. 8-10. 

 Walter Crouch. " Note on Hydrobia jenkinsi." — " Essex Nat.," vol. iv., pp. 



213-214. 

 Ibid. " Hydrobia jenkinsi in Essex." — " Science Gossip," 1891, pp. 163-164. 

 y. W. Williams. "The New Hydrobia." — "Science Gossip," 1890, pp. 



131-132.— Ed.] 



LIST OF SPECIES. 



/. — Fresh JVater and Land Shells. 



Order LAMELLIBRANCHIATA. 



Family SPHyERIIDJE. 



Sphaerium corneum, L. Fairly common ; Plumstead and 

 Tilbury Marshes. 



S. lacustre, Mull. Same localities, and Frith Marshes. 

 Pisidium fontinale, Drap. Local ; Plumstead Marshes. 



Order PECTINIBRANCHIATA. 



Family PALUDINID.E. 



Bythinia tentaculata, L. Common, and generally distributed. 



Var. albida, Rim. One specimen from Coldharbour Marsh. 



B. leachii, Shepp. Common in same locality as B. tentaculata. 



5 See Essex Nat., vol. iv., p. 227, in report of meeting on December 2nd, 1890, when Mr. W. 

 Cole exliihited specimens of Ccccilioidcs acicula from a human skull at East Tilbury. These 

 specimens appear to be recent shell';, and, therefore, il is probable that C. acicula exists on the 

 Essex marshes, although its subterrannean habits enable it, as Mr. Jenkins suggests, to escape 

 detection. — Ed. 



