Bulletins of American paleontology . up to cm in height. Outlines are rounded,varices two per whorl in nearly lateral positions, sutures slightlyappressed, and whorls never tabulate. The straight or slightlyflexed columella bears a thick callous deposit and a variablenumber of transverse wrinkles. Posterior pillar folds and denti-cidations on the outer lip form a pronounced apically orientedexcmrent notch. The commonest forms have reddish brown colorbands parallel to spiral rows of closely set tubercles. Interspacescontain a medial ridge and one or two lateral threads, the overallpattern b
Bulletins of American paleontology . up to cm in height. Outlines are rounded,varices two per whorl in nearly lateral positions, sutures slightlyappressed, and whorls never tabulate. The straight or slightlyflexed columella bears a thick callous deposit and a variablenumber of transverse wrinkles. Posterior pillar folds and denti-cidations on the outer lip form a pronounced apically orientedexcmrent notch. The commonest forms have reddish brown colorbands parallel to spiral rows of closely set tubercles. Interspacescontain a medial ridge and one or two lateral threads, the overallpattern being evenly beaded and striped. Juveniles possess a heavier denticulate varix inside the outerlip and the aperture is smaller in proportion to the overall size. Ashort-haired velvety periostracum covers all but the earliest whorls. Variability. — The more commonly known form, illustrated onPlate 39, figure 2, is more slender and evenly beaded than thesmoother, more inflated variant (PI. 39, Fig. 9). As young forms 464 Bulletin 254. «=» CAPE HORN Argobuccinum ranelliforme (King)• RECENT ? MIOCENE Navidad FormationNear the mouth of the Rio Rapel Text-figure 5. — Distribution ofArgobuccinum ranelliforme (King). Cymatiid Gastropods: Smith 465 the two are similar, and in those that develop tumid outlines andsmoother sculpture these changes take place at different stagesratlier than after a particular number of whorls have specimens commonly have more tumid shells of lowerspecific giavity, although both forms may exceed 8 cm in are completely gradational in many specimens. Axialsculpture or beading may be subdued or lacking in the inflatedvariants in which flat spiral costae are separated by medial ridgesand several sharply incised grooves. The outer lip may be plicate orsmooth and the columella may lack any trace of pillar varices formed by the slightest flaring of outer lips arebarely visible except where the periostracum has be
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Keywords: ., bookcentury1800, bookdecade1890, bookidbulletinsofa, bookyear1895
