Dr. E. von Martens on the Sandwichian Species of Limnzeus. 209 
Limneus oahuensis exhibits no striking difference from the 
general appearance of the European species. LL. volutatus and 
L. Newcombi cannot be compared with any of them. Neverthe- 
less an affinity between the four species cannot well be denied. 
This is another example of the case (frequent in malacology) in 
which a single species seems to offer very strong characters for its 
separation as a genus, while the consideration of all the species 
living in the same country shows its close connexion with others 
in which all the characters of the new genus disappear. Striking 
examples of the same among land-snails are the well-known 
Brazilian Bulimus navicula and the Peruvian Bostryx solutus. 
The sinistral forms have been placed repeatedly in the genus 
Physa. Wow can it be decided whether they are Physe or Lim- 
nei? Our European Physe are distinguished from the European 
Limnai, at first sight, by their sinistrorsity and by the glossy 
-surface of their shell; more essential differences are the long se- 
taceous tentacles and the prolongation of the mantle outside of 
the shell. This latter character does not hold good for P. hyp- 
norum (Aplexa), which according to its other characters is a 
good Physa, and shows by its glossy shell that this lustre is not 
in every case connected with a prolonged mantle. This gloss of 
the shell is absent in the Sandwich species, and also in Physa 
contorta from Southern Europe (Diastropha) and in some species 
from North America. Souleyet has figured the living animal of 
his LZ. affinis. No prolongation of the mantle is to be seen, and 
the tentacles are not long and slender, as in the Kuropean Physe, 
but like those of Limneus. A. Gould refused to rely upon this 
figure, calling it “rather indifferent,” but took for guide only 
the direction of the whorls; so he deseribed (luc. cit. p. 43) a 
Physa reticulata from the Sandwich Islands, the relations of which 
with Limneus struck him and which may perhaps be (I know it 
only from his description) a sinistral form alhed to Lamneus 
oahuensis. The above-described Limneus volutatus sinistrorsus 
is a strong argument, I think, against the practice of calling 
all the sinistral forms Physa. It is true that sinistral specimens 
have been found, but very rarely, among the Kuropean species 
of Limneus (such have been described in the case of L. stagnalis, 
pereger, ovatus, auricularius var. tumidus, and e@ronicus by 
Geoffroy, Held, Hartmann, Forbes and Hanley), and that from 
no other country in the world is a normally sinistral Limneus 
known to us, since Lamarck’s Limneus columnaris is a land- 
snail (Columna flammea). But, on the other hand, it is well known 
that in Transgangetic India and the large islands of the Indian 
archipelago a peculiar group of Bulimus (Amphidromus) is found, 
distinguished by the about equal number of dextral and sinistral 
specimens in most of the species. The Sandwich Islands them- 
Ann. § Mag. N. Hist. Ser, 3. Vol. xvi. 14: 
