HELIX-CALYMNA. 73 



P/eifferia (/) cressida HUTT., Trans. N. Z. Inst. xvi, p. 178, t. 9, 

 f. X, t. 11, f . N (jaw and dentition). Pyrrha cressida HUTT., I. c., 

 p. 200. 



In this species the shell is seen, under the microscope, to be finely 

 obliquely reticulated, the crossing strise having diagonal directions. 

 I formerly mistook it for H. guttula but in that species the shell is 

 described as very smooth, with an inconsiderable, submarginated 

 suture, and the last whorl as callous beneath, in all of which points 

 it differs from our species. 



H. GUTTULA Pfeiffer. (Vol. II, p. 211.) This is said by Suter to 

 be no New Zealand shell, but probably from Mauritius (Trans. N. 

 Z. Inst. xxiv, p. 281). 



Section CALYMNA Hutton, 1883. 



Calymna HUTTON, Tr. N. Z. Inst. 1883, p. 199, -f Amphidoxa 

 Hutton and Suter. Not Amphidoxa Albers, 1850. 



It is difficult to see why the New Zealand species have been 

 referred to the South American group Amphidoxa. I have com- 

 pared specimens of the shells, which seem to be sufficiently distinct ; 

 and we have no reason to believe that the anatomy will prove iden- 

 tical. Those who advocate a former land connection between South 

 America and New Zealand may consider this a sufficient reason for 

 uniting the species of New Zealand and Juan Fernandez in one 

 group, without a comparison of either shells or anatomy ; but con- 

 servative malacologists will demand more evidence before accepting 

 either the malacological or the geographical theory. 



Calymna was proposed to include the species with ribbed whorls, 

 the type being C. costulata Hutton ; but the smoother forms (which 

 New Zealand writers refer to Amphidoxa) will also be included in 

 Hutton's group, as they do not differ in anatomy, and the difference 

 in shell characters is not sufficient for sectional separation. 



A. Whorls ribbed. Typical Calymna. 

 G. COSTULATA Hutton. Vol. IX, PI. 3, figs. 20, 21, 22. 



Shell small, subdiscoidal, umbilicated, shining but not polished, 

 ribbed ; color pale horny, longitudinally banded with reddish, the 

 bands absent on the last half of the last whorl. Spire almost flat, 

 whorls 3J, rapidly increasing, rounded, ornamented with fine spiral 

 striatulations and close ribs, about 40 to 45 in the tenth of an inch, 



