HYVALINIA. 45 
the whorls—a full-grown rvadiatula has 44, while x7tida 
has 5. If, therefore, the shell under consideration is the 
size of an adult vadiatula but has only 3 whorls, the 
observer will know that an extra whorl and a half would 
make the shell too large for a vadiatula, and he may 
conclude it to be a young ze¢zda. 
The animals should also be studied and compared. 
It may be remarked that fulva, crystallina, and excavata 
are unmistakable when their several characteristics have 
been pointed out. 
Sub-genus.—Poura Ffeld. 
I. H. LucipA (clear) Draparnaud. 
[=H. DRAPARNALDI (Beck)]. 
Very slightly convex above ; afex flat, fawn colour above, semi- 
transparent bluish white below; whorls 6-7, finely striated trans- 
versely, last whorl increasing towards the south, which is oval and 
very oblique; zszdcléecus wide. A. 6 mm. B. 14 mm. Azzmal 
cobalt blue all over, including foot-sole ; darker on back, head, and 
tentacles. The mantle shows a dark collar through the shell when 
the animal is out and extended. 
This handsome species, the largest of our British 
flyaliniz, is undoubtedly indigenous, though only 
recently admitted to rank as such. 
The shell when adult is easily distinguishable from 
cellaria by its greater size and flattened appearance, its 
opaque fawn colour, its expansion of the last whorl 
towards the mouth, and its extra whorl. The animal too 
is very distinct in colour. 
