HuTTON. — On the New Zealand HydrobiinsB. 145 



The specimens figured were sent me from Lake Pupake, Auckland, by 

 Mr. T. F. Cheeseman. 



P. COKOLLA. 



Plate I, figs. B and F. 

 Melania corolla, Gould. Pro. Bost. Jour, ii., 1847, p. 

 Amnicula badia, Grould. Pro. Bost. Jour, iii., 1848, p. 75. 

 Hydrohia fischeri, Dunker. Mai. Blatt. viii., 1861, p. 152. 

 Hydrobia reevei, Frauenfeld. Abli. Zool. Bot. Ges. Wien, 1862, p. 1024. 



Shell ovato-conic, reddish-brown or brown, rather solid ; whorls 5 to 6, 

 angulated ; a row of close short spines on the last 2 or 2+ whorls ; usually 

 from 26 to 32 spines on the body whorl. Peritreme continuous or dis- 

 continuous. 



Formula of denticles, „ /, — , ; 11 ; 23 ; 35 to 40. 



' 3 or 4 — 3 or 4 ' ' 



Axis, -15 to -22 inch ; breadth, -13 to -08. 



Habitat : South Island ; abundant in fresh water, Wellington. 



This is a very variable shell in shape, but the whorls are always angu- 

 lated. The spines are always short, but very variable in number ; some- 

 times several are united together, and then the number on the body whorl 

 may not be more than 8 or 10 ; but their compound nature is indicated by 

 their broad flattened base, while in P. cumingiana they are always round 

 and long. This form may be P. salleana, Fischer. The specimens figured 

 are from the Heathcote River, near Christchurch. 



The animal is white, sparingly speckled with black on the foot, body, 

 and tentacles ; more thickly speckled on the head and rostrum ; a paler 

 transverse band near the end of the rostrum. 



The animal does not glide, but moves along by jerks, dragging its shell 

 after. 



Dr. Dunker agrees with Dr. v. Martens that his H. fischeri is only P. 

 corolla with the spines rubbed off, which is no doubt true. A. badia, Gould, 

 and H. reevei, Frauenfeld, are certainly the same as H. fischeri. 



P. ANTIPODUM. 



Plate I., figs. C and G. 

 Amnicola antipodum, Gray. Dieffenbach's New Zealand, 1843, p. 241. 

 Amnicola zealandicB, Gray, I.e., p. 241. 

 Amnicola egena, Gould. Pro. Bost. Jour, iii., 1848, p. 75. 

 Amnicola gracilis, Gould. Un. States Ex. Exp., p. 126, fig. 150. 

 Hydrobia spelcea, Frauenfeld. Abh. Zool. Bot. Ges. Wien, 1862, p. 1022, 



Shell ovate, blackish-brown to olive-green, rather solid ; whorls 5 to 6^, 

 rounded, smooth ; aperture ovate, peritreme continuous or discontinuous. 



Formula of the denticles, '^ ; 9 ; 23 ; 35 to 40. 



Axis, -24 to '16; breadth, -12 to -09. 



