Suteb. — Species of the Genus Potamopyrgus. 261 



corolla, Gould (1847), is not corolla of Hutton, but the shell 

 figured by Reeve as corolla. It is the largest, with spare long 

 spines. The locality may have been erroneous. The whorls are 

 rounded, cf. Hutton, Trans. N.Z. Inst., vol. xiv., pi. i., fig. A 1." 

 Considering this statement, we must conclude that the synonyms 

 given by Hutton in his Manual, p. 83, are mostly correct, but 

 that in his revision he took the wrong species for corolla — viz., 

 Amnicola badia, Gould. He says (I.e., p. 143) that P. cumingiana, 

 Fischer, which is held by v. Martens to be the same species as 

 P. corolla, Gould, does not occur on Banks Peninsula, and that 

 its dentition does not correspond with the description given 

 by Dr. Stimpson. Now, Dr. Dall admits that the locality given 

 by Gould may have been erroneous, and this appears now to 

 be quite certain. I examined the dentition in typical specimens 

 of P. corolla from the Ruamahanga River, Wairarapa, and I 

 cannot say that it does not agree with Stimpson's description. 

 The rhachidian and the lateral teeth correspond with his diag- 

 nosis, but the marginal teeth have a number of larger denticles, 

 their number agreeing with Stimpson's statement, but there 

 are a number of minute denticles besides which I am unable 

 to count with a magnifying- power of 720. The number of den- 

 ticles on the marginal teeth is variable, and can hardly be used 

 for specific distinction. 



The diagnosis of the species is as follows : Shell horn-colour, 

 sometimes covered with a black coating, ventricose, thin, sub- 

 pellucid ; 6J rounded whorls, the last three spinous, the others 

 smooth and sometimes of a darker colour, the last swollen, 

 subcarinated at the encircling series of spines. Spines long, 

 rather distant, curved, directed upwards. Aperture ovate, peris- 

 tome continous, thickened. There may be only rudimentary 

 spines, or they may be absent altogether, leaving only a carina, 

 or, finally, all the whorls may be smooth and convex, without a 

 trace of a carina or spines. Length, 6*5 mm. ; breadth, 4*5 mm. 

 Ratio of B: L = 1: P44. 



This species is distinguished by its globosely ventricose form, 

 the absence of spines on the first 3| whorls, the great number 

 of spines on the last whorl (17 to 20), their length, curvature, 

 and direction towards the apex. 



My collection contains specimens from fourteen localities : — 



(1.) Typical form with long spines is represented from Lakes 

 Takapuna and Kanieri. Those from the latter locality have 

 shorter spines. Most of the specimens are of horn-colour, some- 

 times with the first few whorls darker, and a few have a dark- 

 brown coating. 



(2.) Specimens with rudimentary spines occur in the creeks 

 at Henderson and Swanson ; in the creek at Hastwell's and 



