HORSLEY : PRESIDENTIAL ADDRESS. 53 



oval Var. ponderosa is heavier from the soHdity of its shell. Alar- 

 garitatui from the Greek for a pearl. The species margaritifer = 

 pearl-bearing. Its var. sinuatci, i.e. curved, has the lower margin of 

 the shell incurved. 



The genus Anodonta is named from the absence of lateral teeth at 

 the hinges. A. cygncea and A. anatina were so named by Linne as 

 eaten by swans and eaten by ducks respectively. Scliroter's variety 

 arenaria probably means " found on a sandy bottom." Var. rostrata 

 = beaked ; var. incrassata=-\}mQk.&w&di. 



The genus SphcBriuvi {ce not ce) is so called from the spherical or 

 rounded character of the shell. S. co7-tieum var. nucieus is especially 

 suggestive of a ball. Gray's var. pisidioides gets its name from being 

 somewhat triangular like tlie Pisidia. Rivicola^iviS\dXy\\\\\% rivers. 

 Cor7ieti7n=\\ox\v^ in colour. Lacusire lias a var. ryckhoiti, named 

 after Baron P. de Ryckholt. The type is round, but var. rotunda is 

 more round, and var. ovalis more oval than the type. Pallidum is 

 pale grey. 



The genus Pisidiiim was named from its likeness to a pea, pisutn in 

 Latin. The species avinicum is named from its inhabiting rivers. 

 The var. Iceviuscula is, I presume, bad Latin and bad spelling for 

 levior, i.e. smoother, the striae being faint. Ifenslowanuin was 

 named by Sheppard in honour of Prof. J. S. Henslow, of Cambridge 

 ( 1 796-1 86 1 ) j subtruncatu/n, somewhat truncated ; pulchelhim is glossy 

 and therefore perhaps more worthy of its name "pretty little one" ; 

 pusillum, i.e. small; nitiduni, i.e. shiny, is the most glossy of its con- 

 geners; obtusale, i.e. blunt; gassiesianum was named after M. Gassies, 

 a contemporary French conchologist who collected chiefly in New 

 Caledonia. 



Note. — I find that I was misled as to the quantity of the / in Arion 

 (see p. 19, line 27), and that it is long after all. 



Helicella virgata at Lowestoft. — On the 21st January of this year this species 

 was crawling freely on a sloping bank of the south promenade at Lowestoft. Quite 

 twenty-five per cent, were of the varieties alba and hyalozonata, a larger proportion 

 than I have seen anywhere else, except near Dublin. — W. Gvngei.l {Read before 

 the Society, Sept. nth, 1912). 



