456 MOLLUSCA or the ANDAMAN AND NICOBAR ISLANDS. [May 21, 



distinct transverse fine ribbing is seen, and on breaking a mature 

 shell back to the same number o£ whorls as in so-called Saydinella 

 a precisely similar form of shell A^as presented. Moreover, this 

 Pupina, at the commencement of the fifth whorl, contracts very 

 considerably and the shell is perforate at this stage. On turning 

 to the original description I see that Professor Miirch described it 

 from a single example, and T can quite understand his being misled 

 by this peculiar young form, so vei-y unlike the typical mature 

 shell in Pu^nna. I note that in this white very thin variety every 

 gradation can be seen from shells quite glassy to others most dis- 

 tinctly ribbed. The dra\^'ing of Sagdinella didrichseni given on 

 plate ix. figs. 1, 1 «, in my ' Land and Freshwater MoUusca of India,' 

 was made from the type specimen sent to me from the Copenhagen 

 Museum. 



Helicina. 



Nevill gives many varieties and subvarieties of the species of 

 this genus, particularly of //. andamanica and H. serupulum ; he 

 recoi'ds that the animal of II. andamanica from Mount Harriet, 

 Port Blair, " is of a mottled dark grey colour, sparsely dotted with 

 sand-like specks, base of the tentacles yellow," 



List of Genera and number of Species. 

 Helicacea. 



