2l8 JOURNAL OF CONCHOLOGY, VOL. I3, NO. 7, JULY, I9II. 



Papers Read. 



'■'■Helix ucmoralis and //. hortensis : Tlieir Colour and Band Variations and 

 Distrihulion," by W. Gyngell. 



'■'■ Diloma nigerrimitm Gmel. on the Coast of Chile," by J. E. Cooper. 



"New County Records for Pisidhuii,'" by J. E. Cooper 



Mr. W. M. 1'attersall, M.Sc. gave an interesting address, embodying the 

 results of some original researches into the Eife-History of Lil/oiiiia liliorca. 



Exhibits. 



By Mr. W. M. Tattersall : A large series of the British species of I.i/torina, 

 showing extremes of variation in size and colour in different localities, to illustrate 

 his address upon the Life-Ilistory of Littorina Uttorea. 



By Mr. R. Cairns : A series of varieties of Cypriea staphyhea ; also C. capiit- 

 draconis, C. iiigiopunctata, C. dtn'tia, and many other rare species among the 

 smaller forms. 



By Mr. R. Standen : Planorbis corneiis taken near Manchester ; sets obtained 

 from one pond during a number of consecutive years, showing a gradual change from 

 typical horn colour, through straw colour to white, and on to normal form again. 



By Mrs. Gill : A fine set of Trigonia from Australian localities ; and a number 

 of bivalves polished to show outer structure of shell. 



By Mr. J. E. Cooper : Diloma iiigeniiinim Gmel. from Chile ; Pisidittm 

 ptilchelltDU from Southwold, P. persoiiatitin from Hampslead, Arthog, and Llyfnant 

 Valley. 



Si'EciAL Exhibit. 



The chief exhibit of the meeting was a large and comprehensive collection of 

 British UnioiiidiT, probably the finest series ever brought together in the British 

 Isles. Besides the Manchester Museum collection (R. D. Darbishire coll.), large 

 series were shown belonging to the Conchological Society (Oldham coll.), and 

 from the private collections of Messrs. J. Wilfrid Jackson and R. Standen. In- 

 cluded with the latter were fine series illustrating the Life-History of Atiodonta 

 cygfuta, from the glochidium to the adult. 



Specimens of various locality sets of Ujiio and Anodoiita were also exhibited 

 by Messrs. T. H. Piatt, J. Ray Hardy, F. Booth, G. C. Spence, F. Rhodes, J. 

 Madison, W. D. Roebuck, and Mrs. Gill. 



During the meeting. Miss Margaret C. IMarch, who has been studying the 

 British Unionid(t at the Manchester University, gave a most interesting account 

 of the variation in the. shells of Unio pictortim, U. tiiniidiis and Anodoiita cygiura, 

 which was listened to with great attention. 



The points dealt with by Miss March are eml)odied in the following abstract : — 



A. — Effect of environment : i.. Marls or clays tend to produce animals with thick 



bodies and shells. ii., Current action in lock basin produces anteriorly 



truncated forms, with a forward throw of the umbo. iii.. Animals living 



in water with excess of lime and absence of humic acid have thin shells. 



iv. , The loss of the wing during the growth of Anodoiita cygiura can be 



shown to be due to wearing. 



r>. — Variation in umbonal markings : i., The three types of umbonal marking in 



Unio pictortiin, U. iuiiiidiis, and Anodoiita cygmra grade into one another. 



U. iuinidus appears to retain the least degenerate type, and therefore to be 



the most primitive. This is supported by the state of development of its teeth. 



C.^ — Relationship of British Freshwater UnionidiE : The intermediate stages 



between the Uiiioiies and Anodoiita, can be filled in from American forms, 



giving k perfectly graded series, from [/. Iuinidus through U. pictormii to 



A. cygitica. 



