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New bathymetric and magnetic anomaly data from the Phoenix Ridge, Antarctica, show that extinction of all three remaining segments occurred at the time of magnetic chron C2A (3.3 ± 0.2 Ma), synchronous with a ridge-trench collision south of the Hero Fracture Zone. This implies that the ultimate cause of extinction was a change in plate boundary forces occasioned by this collision. Spreading rates slowed abruptly at the time of chron C4 (7.8 ± 0.3 Ma), probably as a result of extinction of the West Scotia Ridge, which would have led to an increase in slip rate and transpressional stress across the Shackleton Fracture Zone. Spectacular, highrelief ridges flanking the extinct spreading center, mapped for the first time using multibeam swath bathymetry, are interpreted as a consequence of a reduction in spreading rate, involving a temporary magma oversupply immediately prior to extinction.

We report the occurrence of idiopathic eruptive macular pigmentation in four children and one adolescent. This condition appears to be a distinct clinicopathologic and histologic entity. It is characterized by asymptomatic, pigmented macules involving the neck, trunk, and proximal limbs. All patients or their families denied the patients' having taken any drug before the eruption. In all of the patients the first sign was a pigmented spot without preceding erythematous, papular, or hypopigmented lesions. Histologic study showed enhanced epidermal basal layer pigmentation with pigmentary incontinence, a mild perivascular lymphohistiocytic infiltrate, and many melanophages in the papillary dermis. Electron microscopy showed an increased number of melanosomes in basal and suprabasal keratinocytes as well as clustered melanosomes in dermal melanophages. Treatment of this asymptomatic condition is unnecessary because spontaneous resolution of the lesions is to be expected within several months to a few years.

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