Bulletins of American paleontology . to 32°45N and F. galea from 35° N to approxi-mately 30°N; F. midwayensis occurs at 35°15N, 171°50E. BIOGEOGRAPHY OF FUSITRITON IN THE SOUTHERN HEMISPHERESpecies boundaries for the three taxa recognized here coincideconveniently with large geographic areas when only a few lots ofspecimens are considered and mid-ocean assemblages of several tens of lots showed considerable morphologicvariation in material from South America, South Africa, and Aus-tralia-New Zealand. In each broad area there are at least two if notthree variants, one of which r
Bulletins of American paleontology . to 32°45N and F. galea from 35° N to approxi-mately 30°N; F. midwayensis occurs at 35°15N, 171°50E. BIOGEOGRAPHY OF FUSITRITON IN THE SOUTHERN HEMISPHERESpecies boundaries for the three taxa recognized here coincideconveniently with large geographic areas when only a few lots ofspecimens are considered and mid-ocean assemblages of several tens of lots showed considerable morphologicvariation in material from South America, South Africa, and Aus-tralia-New Zealand. In each broad area there are at least two if notthree variants, one of which resembles specimens from the otherregions. Text-fig. 15 is a map showing the distribution of F. can-cellatus, F. c. Marrayi and F. retiolus. Points represent one ormore lots from each locality, species having been determined byshell morphology. Material from 54°49S, 129°48W (EltaninCruise 15, Sta. 1346) sliares morphologic characters with botheastern Pacific and western Pacific species, although it is treated 530 Bulletin 254. SCALEApprox. I: 150,000,000 Text-figure 15. — Biogeography of Fusitriton in the Southern denotes occurrences of Fusitriton cancellatus (Lamarck), • murrayi(Smith), and A F. rctiolus (Hedley). here as F. cancellatus. This prevalance of morphologic overlap isprobably explained by a nearly continuous circumpolar distribu-tion in the southern ocean and by speciation that is relativelyrecent or in progiess. In terms of latitude, F. cancellatus ranges from 32° 17 S to 55°S, F. c. murrayi from 29° 17 S to 35°3 S, and F. retiolus fromapproximately 33°30 S to 51 °S, 166-E. Barriers such as currentsflowing in opposite directions or abrupt temperature changesare not present near the northernmost occurrence of F. cancellatusoff western South America, which suggests that future collectingmay extend this range. Cymatiid Gastropods: Smith 531 BIOGEGGRAPHY OF RECENT SPECIES OF ARGOBUCCINUMIN THE SOUTHERN HEMISPHERE Five species of Argobuccini
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