262 Transactions. — Zoology. 



Ruamahanga River in the Forty-mile Bush ; at Petone, near 

 Wellington ; Parua Bay, near Whangarei ; and on the Chatham 

 Islands. The majority of these specimens have a thick, black 

 coating, and the continuous peristome much thickened. 



(3.) With only a thread-like carina on the whorls there are 

 specimens from Hastwell's and the Chatham Islands. 



(4.) Shells with the whorls smooth, rounded, mostly coated 

 with black and callous peristome, were found in creeks at North- 

 cote, Hastwell's, Parua Bay, Kawau Island, the Waikato, and 

 Chatham Islands. 



(5.) Dwarf forms with spines, horn-colour, and six whorls, 

 were collected in Lake Takapuna (3| x 4^ mm.), and near 

 Greymouth (4 x 6 mm.). 



Type in the U.S. Nat. Mus., Washington. 



Potamopyrgus corolla, Gould, subsp. salleana, P. Fischer, subsp. 



Paludestrina salleana, P. Fischer, Journ. de Conch, vol. viii. 



(1860), pp. 208, 209, pi. iv., fig. 6. 



Shell horn-colour, conical, thin ; whorls 7 to 7-1, flatly con- 

 vex, the last four spinous, the others smooth, the last whorl 

 with a chordate carina below the row of spines. The setae are 

 short, black, directed upwards. Aperture ovate, margins con- 

 tinuous, but little callous. Length, 6 mm.; breadth, 3^ mm. 

 Ratio of B:L = 1 : 17. 



This subspecies differs from corolla in being more slender, 

 less ventricose, in having spines on the last four whorls and a 

 chordate carina below the row of spines ; the last whorl is also 

 less voluminous in proportion. 



Although I have examined many hundreds of specimens I 

 have not yet seen one with a chordate carina below the row of 

 setse, but some specimens from the Great Barrier Island and from 

 Nelson are distinctly angled below the periphery, and I take 

 this quite peculiar character mentioned by Fischer as of quite 

 exceptional occurrence. 



The distribution of this subspecies extends over a large area. 

 In my collection there are specimens from Lake Takapuna, 

 Western Springs (Auckland), Lake St. John, Onehunga Springs, 

 Great Barrier Island, Maketu (Hunua Range), Waipoua River 

 (near Masterton), Petone (near Wellington), Pelorus River, Nel- 

 son, and Collingwood. 



All specimens are yellowish-brown, thinner than corolla. 

 mostly without spines, and some are larger than the type. 

 Length, 8 mm. ; breadth, 41 mm. The Nelson specimens are 

 from brackish water. 



Type in the collection of the Journal de Conchyliologie, 

 Paris. 



