274 



Transactions. — Zoology. 



6 mm. Mean rationis — 1. = 1 : 1*7 ; ii. = 1 : 2 ; iii. = 1 : 1*5. 

 These specimens are slightly more ventricose and have the 

 aperture in proportion shorter than the type. 



Hab. Lake Hayes, Otago ; near Napier ; Lake Wakatipu. 



Type in Mr. Sowerby's cabinet (?). 



Isidora lirata, Tenison- Woods (1879), sp. 



Physa lirata, T.-Woods, P.L.S. N.S.W., vol. iii. (1879), p. 138, 

 pi. xiii., fig. 6. Physa lirata, Hutton, Man. N.Z. Moll., 

 p. 31 ; Trans. N.Z. Inst., vol. xvii., p. 57. Bulinus liratus, 

 Hedley and Suter, P.L.S. N.S.W. (2), vol. vii., p. 627. Bulli- 

 nus liratus, Suter, Journ. de Conch., vol. xli., p. 233. 



The diagnosis is also in Hutton's Manual, and the accom- 

 panying fig. 6 is reproduced from T. -Wood's figure. 

 Fig. 6a shows a few teeth of the radula : the 

 rhachidian tooth is bicuspid, the laterals tricuspid, 

 the following transition teeth with four and more 

 denticles, and the marginals are elongate and 

 serrate. 



This is one of the best-characterized species ; 

 the fine spiral lirae and the anteriorly produced lip 

 distinguish it at once from all the other New Zea- 

 land species. The dimensions given by T.-Woods 

 are — Shell : length, 10 mm. ; breadth, 5 mm. 

 length, 5 mm. ; breadth, 3 mm. The proportions 

 1:2; ii. = 1 : 1-7 ; iii. = 1:2: but taken from the 

 figure we get — i. = 1:1-9; ii. = 

 1:2-2; iii. = 1: 15. 



In my collection the species is 

 represented from twelve localities : 

 Rivers Heathcote and Avon, creek 

 Fig. 6a. in St. Albans, pond in Fendalton, 



all near Christchurch ; Wellington ; 

 Greymouth ; Pelorus River ; pond near Lake St. John ; Toko ; 

 Lakes Virginia and Westmere, near Wanganui ; and North 

 Island, exact locality unknown. The specimens vary a great 

 deal in size and proportions, but the main features mentioned 

 above are always present. The colour is usually light-horny, 

 the whorls are sometimes smooth but mostly strongly carinated, 

 and the carina usually adorned with short light-brown bristles, 

 a character only met with in this species. 



I measured altogether thirty-one specimens and found the 

 rationis to vary — i., from 1:1-6 to 1 : 1-9 ; ii., from 1:1-6 to 

 1:2-4; iii., from 1 : 13 to 1 : 1'7. The means are as follows — 

 i. = 1 : 1-7 ; ii. = 1 : 19; iii. = 1 : 15. 

 Type where ? 



Fig. 6. 



Aperture 

 are — i. = 



{£P 



