Dr. E. yon Martens on the Sandwichian Species of Limnezeus. 207 
water of the estuary of the Yangtsekiang, and I have also found 
a Bulla in company with Assiminea in a muddy inlet at Macao, 
this consideration seems to give some reason for suspecting 
Laguncula pulchella to be an Asstminea. 
Paludina pulchella, Hutton, from British India, seems to be 
distinct from this Chinese shell; but it resembles, in common 
with some nearly allied species from the same country, some 
Assiminee, by the keel in the base of the shell; the operculum, 
however, as well as the outer appearance of the shell, are those 
of Bithynia; and it seems to inhabit, like this latter genus, 
really fresh water. 
Finally, it ought to be observed that, in order to ascertain the 
length of the tentacles and the position of the eyes in a living 
mollusk of amphibious habits, it will be as well to observe it both 
in the air and when surrounded by water. An example will 
show how mistakes may occur. In the ‘ Voyage of H.ML.S. 
Samarang’ (a work which has contributed so largely to our know- 
ledge of living mollusks), pl. 18. fig. 3 a, Cerithium obtusum, a 
relatively large mollusk, is figured with short tentacles and the 
eyes at their tips, just as in Assiminea, and the description at 
page 44 says exactly the same. Such is, indeed, the appearance 
of the living animal when seen out of the water; but if observed 
in water, the long slender portion of the tentacle is instantly 
seen to be prolonged far beyond the eye, as in all other Cerithia; 
the apex must have laid ciose to the base when the animal was 
out of the water, as I have repeatedly seen in Singapore. 
Ill. The Sandwichian Species of Limneus. 
So far as I am aware, only four species of Limneus are re- 
corded in different malacological works as living on the Sand- 
wich Islands, —Z. oahuensis and affinis, Souleyet, L. sand- 
vicensis, Phil., and L. volutatus, Gould. Three species are con- 
tained in the Berlin Museum, a comparison of which with the 
existing descriptions and figures has led me to the following 
results :-— 
1. Limneus oahuensis, Souleyet, Voyage de la Bonite, Zool. 
(1841) vol. ii. pl. 29. figs. 38-41.  L. sandvicensis, Philippi, 
Wiegmann’s Archiv fiir Naturgeschichte, 1842, figured in 
Kiister’s new edition of Chemnitz, Limneeacea, pl. 4. figs. 25, 26, 
does not offer any specific difference. Oblong-ovate, with rather 
convex whorls; columellar plait moderate. 
2. Limneus affinis, Souleyet, loc. cit. figs. 42, 44. Sinistral, 
ovate-globose ; the whorls convex, the upper ones worn off. 
3. Limneus volutatus, Gould, Expedition, Shells, p. 41 
