174 THE VOYAGE OF H.M.S. CHALLENGER. 



This interesting species is regularly rounded, some\Yliat narrowed in front and 

 obliquely truncate behind. It is rather solid, considerably inec[uilateral, moderately 

 convex, and whitish beneath a dirty yellowish epidermis. The sculpture consists of thin 

 elevated lamellae which are anteriorly less developed than upon the central portion of the 

 valves, which exhibit a shallow depression down the posterior side, a little below the 

 dorsal margin, gi^ang the concentric lamellae a somewhat flexuous appearance at this part. 

 The interstices between the lamellae are rather roughly striated. In front of the acute 

 umbones the valves have a deep lanceolate elongate lunular excavation defined by very 

 sharp edges. The front dorsal outline is slightly concave, very oblique, and rather 

 shorter than the posterior, which is a little convex and not nearly so sloping. The lower 

 margin is well curved, and ascending obliquely in front, forms together with the dorsal 

 line a sharply rounded pouting extremity. The hinder end is obliquely truncated, the 

 shallow dejjression terminating in the middle of the straight edge which joins the dorsal 

 and ventral margins in rounded angles. The ligament is strong, and placed in a deep 

 groove occupying the entire length of the hinder dorsal margin, but does not project 

 above the upper edge of the valves. The interior, with the exception of the hinge-line, 

 muscular scars, pallia! line, and outer margin, which are glossy, is chalky white, roughish 

 and subpunctate. The anterior impression is very long and narrow, and falls ol)liquely 

 within the pallia! line almost to the centre of the valves. The 2:)Osterior is nearly twice 

 as broad, of an irregular oval form, and radiately striated. The hinge consists of two 

 cardinal teeth and a single lateral in each valve. Of the former, the posterior in the 

 right and the anterior in the left are bifid, and the lateral tooth is small and tubercu- 

 liform. 



Length 47 mm., height 42, diameter 24. 



Length 39 mm., height 36, diameter 16. 



Hahitat. — Station 311, western part of the Strait of Magellan, at a dearth of 245 

 fathoms ; blue mud. 



This species I originally described as a Dvplodonata, having overlooked the presence 

 of the anterior lateral tooth, which in the young shells then at hand was very incon- 

 spicuous, and indeed in the adult specimens obtained by the Challenger consists merely 

 of a slight tuljereular projection. The types were dredged by Dr. Coppinger of H.M.S. 

 " Alert," in Portland Bay, St. Andrew's Sound ; also on the west side of Southern 

 Patagonia, in 10 fathoms, on a liottom of hard sand. 



Lucina ramsayi, n. sp. (PI. XIIL figs. 2—26). 



Testa mediocriter convexa, subseciuilateralis, rotundata, solidiuscula, allja, concentrice 

 confertim lirata, striis radiantibus in interstitiis subpunctatim sculjjta. Lunula parva, 

 profunda. Margo dorsi anticus leviter concavus, posticus vix declivis, superne recti- 



