Sutek. — Species of the Genus Isidora. 271 



I have examined and measured specimens in my collection 

 from the following localities : — 



(1.) Ditch near Lake Takapuna, Auckland. The specimens 

 are fuscous, with a ferrugineous coating, shouldered, larger and 

 more slender than the type. Two specimens measured gave 

 length of shell 15 mm. and 17 mm., breadth 9 mm. ; and the 

 mean proportions were found to be — i. = 1 : 18; ii. = 1:2; 

 iii. = 1 : 1-7. 



(2.) From Lake Takapuna, Auckland. Two specimens, dark- 

 brown, strongly carinated, larger and a little less ventricose 

 than the type. Shell : length, 12-15J mm. ; breadth, 7-9 mm. 

 Mean rationis — i. = 1:1-7; ii. = 1 : 2 ; iii. = 1 : 15. 



I first tried to uphold I. coromandelica, Dunker, as a separate 

 subspecies of /. tabulate, as the specimens of the above three 

 localities approach the ratio between breadth and length of shell 

 of /. coromandelica, which is 1 : 2, but I soon found out that 

 all intermediate forms, from the elongated coromandelica to the 

 more ventricose moesta, are met with, and, as there seems to be 

 no other character available to distingusih the two, I thought 

 it advisable to make the former a synonym of the latter. 



(3.) Wanganui (no exact locality). One adult and two not 

 quite full-grown specimens were measured. The adult had — 

 length, 17 mm. ; breadth, 10 mm. All specimens are shouldered. 

 The mean proportions are — i. = 1:1-6; ii.= 1 : 2 - l ; iii- = 1 : 1*4. 



(4.) Fresh-water stream, Parua Bay, Whangarei. All speci- 

 mens are blackish-brown, two are distinctly shouldered, the 

 other has smooth whorls. The columellar fold is very distinct. 

 Three shells showed the length to vary from 9-15 mm., the 

 breadth from 5|-9i mm. The mean proportions are — 1 = 1:1-7; 

 ii. = 1:1-9; iii". = 1:1-6. 



(5.) Waikato River, near Huntly. 'Shells of good size, 

 chestnut-colour, some with a ferrugineous coating ; young 

 specimens are strongly carinated, in adult specimens the carina 

 is reduced to a slight angulation on the last whorl. Columella 

 strongly twisted. Four shells were measured, the length being 

 12-15 mm. ; breadth, 8-11 mm. The mean proportions were— 

 i. = 1:1*4; ii. = 1 : 1-9 ; iii. = 1 : 1*6. 



(6.) Chatham Islands. One specimen only, of yellowish- 

 brown colour, with four shouldered whorls, this is a slender 

 form. Length, 8 mm.; breadth, 4| mm. Rationis — 1 = 1 : L8; 

 ii. = 1 : 2 ; iii. = 1 : 1-6. 



The result of measuring twenty-eight specimens is the fol- 

 lowing : Ratio i.— variability, 1 : L4 to 1 : 1-8 ; mean, 1 : 1'65. 

 Ratio ii.— variability, 1 : 1-9 to 1 : 2-3 ; mean, 1 : 2. Ratio in- 

 variability, 1 : 1-4 to 1 : 1-7 ; mean, 1 : 15. It shows that the 

 shells of this subspecies are a little more slender and the spire 



