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ased on a genus name. This leaves 2,060
names that meet the criteria of availability. Of
these, 113 are permanently invalid, mainly
because the type genus is a junior homonym;
when these are eliminated, there are 1,947
names that are potentially valid (Fig. 1 ).
An analysis of the year of publication of the
2,060 available names shows (Fig. 2) that, on
average, 12.3 names have been established
yearly since 1850. Three periods are above
average: a brief, low peak in the 1850's; a
second, much higher, sustained peak in the
1920's-1930's, when a record total of 377
names where established in just 20 years; and
a third one, broader and regularly rising since
the 1950's, marks modern times.
The first peak corresponds to Gray's prolific
writing, notably his Figures of molluscous animals
(1850b), Catalogue of Phaneropneumona
(in L. Pfeiffer, 1853a), Division of
ctenobranchous gasteropodous Mollusca
(1853a), Catalogue of Pulmonata (1855),
Guide to the systematic distribution of Mol-
250
200
150-
100-
50-
NOMENCLÁTOR OF GASTROPOD FAMILIES 13
lusca in the British Museum (1857a); to H. &
A. Adams' Genera of Recent Mollusca
(1 8531 858); and to Troschel's Das Gebiss der
Schnecken (1857-1858). The intervening
years saw the publication of Paul Fischer's
Manuel de conchyliologie et de paléontologie
conchyliologique (1880-1887); Cossmann's
Essais de paléoconchologie comparée (1 895-
1924); and Pilsbry's prolific writing, including
the second series of the Manual of conchology
(1892-1926). The second peak is the re-
sult of many more authors and publications,
but particularly active in these years were H.
B. Baker, Iredale, Odhner, Pilsbry, Thiele, and
Wenz, with landmark works by Thiele, the
Mollusca part of Kükenthal & Krumbach's
Handbuch der Zoologie (1925-1926), leading
to the Handbuch der systematischen
Weichtierkunde (1929-1931); and by Wenz,
the land snail parts of Fossilium Catalogus
(1 923-1 930) and the "Prosobranchia" part of
Schindewolf's Handbuch der Paläozoologie
(1938-1944). After World War II, which bites
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oooooooooooo -'^^-- ooooooooo \1'!-^>
^----------- aJCDCDCDCDCDCnOO
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FIG. 2. Number of available names (total 2,060) published during
each decade since 1800.