1927] _ Pulsbry-Bequaert, The Aquatic Mollusks of the Belgian Congo 169 
because two years later he added the words “muni d’un opercule corné.”’ 
This is a pure assumption; in many cases an author has subsequently 
amplified his generic diagnosis by adding characters from additional 
species, and this is obviously what Lamarck did. So far as we have been 
able to learn, N. urceus was never known as “le cordon bleu.” We be- 
lieve that, in cases where an author bases a genus upon a described 
species and there is nothing in the original diagnosis to show that he 
meant something else, neither he nor any other author has the right to 
shift the generic name to any other genotype. Ampullaria Lamarck 
will therefore become Pila Réding, both having the same type. 
Key to the Known Genera and Subgenera of Ampullariide 
l. Shell: dextran gic vce ae Pe a ae dt Ne Senn ee 2. 
Shell sinistral. Operculum corneous, very thin. Africa. Lanistes Denys de 
Montiottiic: 437. as Pe Py GR ays ohio bem Seay ee tetas oN 5 G14 ale § Apr ean Re gaa 9. 
2. Operculum thick and internally calcareous. Old World tropics. Pila Réding.3. 
Operculum. thin and wholly semeoue. 606.600 ee ee a 4. 
3. Umbilicus closed; the columella with a narrow, flat callus. Radula with the 
lateral cusps of the teeth reduced or vestigial. India. 
Subgenus Turbinicola Annandale and Prashad.2 
Umbilicus perforate or broadly open, rarely vestigial; the columella not calloused. 
Subgenus Pila, proper. 
4. New World topasse:0:. ei ie er cas eee kee ce alates 5. 
Old Work Formigs css Ve Mie i ee Nine Bhp wr hf pre ey e ece ieCe 8. 
5. Left epipodial lobe (respiratory siphon) very long. Pomacea Perry?........ 6. 
Left epipedial tobe very elvan? i iiiors See ety ee eRe ae ‘es 
6. Form elevated, the umbilicus narrow or sometimes closed. 
Subgenus Pomacea, proper. 
Form depressed, the umbilicus broadly open...Subgenus Marisa J. E. Gray. 
Form planorbeidhe i.e Sra tee ee ee Subgenus Ceratodes Guilding. 
7. Shell globose, compact, solid, and smoothish............. Asolene d’Orbigny. 
Shell hemispherical, of few, very rapidly increasing whorls, the last roughly 
sculptured, Very eapacious. 2c ee Pomella Gray.® 
1Nerita urceus was known as “‘l’idole’’ in old French works using the vernacular names. Prior to 
Lamarck’s use of the term in 1799, ‘‘le cordon bleu”’ was the name given to snails identified by Chemnitz 
and others with Helix ampullacea Linneus. See Martini and Chemnitz, 1786, ‘Syst. Conch. Cab.,’ 
IX, pp. 105-109. At the time Lamarck mentioned ‘‘ Ampullaria ampullacea, le cordon bleu,”’ that was 
one of the best known species of the Ampullariide, from its appearance in Chemnitz’s widely used 
iconography. See also Lamarck, 1822, ‘Hist. Nat. Anim. sans Vertébres,’ VI, 2, p. 177. 
21921, Rec. Indian Mus., XXII, p. 9. Monotype: Ampullaria nux Reeve=Ampullaria saxea 
Reeve. See Prashad, 1923, Journ. Proc. Asiat. Soc. Bengal, N.S., XVIII, (1922), p. 591. 
sThe group Limnopomus Dall, proposed as a subgenus of Ampullaria Lamarck, and characterized 
by the imperforate axis and heavily calloused columella, cannot be exactly placed until the form of its 
siphon is known. We therefore leave it where originally placed, though we strongly suspect that it will 
prove to be brevisiphonate, and a subordinate group of Asolene. ont 
4Marisa J. E. Gray, 1824, Philos. Mag. and Journ., LXITI, p. 276. Monotype: Marisa intermedia © 
J. E. Gray, of Brazil, probably the same as Ampullaria intermedia Férussac, 1824 (?), ‘Voy. Uranie, 
- Zool.,’ p. 489; Atlas, Pl. tyxvi1t, figs. 1-3. . ina 
5The type of Pomella, Ampullaria megastoma Sowerby, was found to have a very short siphon by 
Doello-Jurado (1915, Physis, II, p. 39). 
