MOLLUSCA OP THE ' CHALLENGER EXPEDITION". 259 



St. 33. April 4, 1873. Lat. 32° 21' 30" K, long. 61° 35' 55" 

 W. Bermudas. 435 fms. Coral-mud. 



Shell. — Strong, conically globose, with a high scalar spire, 

 laterally compressed, so that its outline is peculiarly square ; 

 mouth small ; umbilicus open, deep, and f uniculate. Sculpture. 

 Longitudinals — there are many, unequal, but generally fine lines of 

 growth, which are strong above, and there radiate like curved 

 spokes from the suture ; they are sharpest and highest on the 

 earlier whorls ; on the base they are again, stronger, and on the 

 edge of the umbilicus they are sharply bent back, and form there 

 an indistinct carina. Spirals — the whole surface is covered with 

 very faint and narrow obsolete lines and furrows, over which is a 

 minute system of sharp microscopic scratches. Colour polished 

 porcellanous white, with an indistinct and indefinite staining of 

 buff below the shoulder and round the outside of the umbilicus. 

 Epidermis : within the umbilicus are remains of a rather strong, 

 thinnish, smooth, but puckered, blackish-yellow membrane. 

 Spire high, scalar. Apex large, tumid, but with the extreme tip 

 a very little bent down. Whorls 5, of which 1| are embryonic 

 and glossy, rounded and rising high, each above the preceding one ; 

 they are laterally compressed so as to give a peculiar character to 

 the shell, which is angulately shouldered below the suture, and 

 tumid and broad at the base. Suture oblique, impressed, but not 

 channelled. Mouth very small for the genus, very oblique, semi- 

 circular, but reduced by the large superior labial pad to a flat- 

 sided oval, deep, not open; its height is less than three fourths 

 that of the whole shell. Outer lip narrow, but strong; it rises a 

 very little at its junction with the body, retreats a good deal 

 throughout its whole very equable sweep, till on the base towards 

 the point of the pillar it very slightly advances, and there alone is 

 a very little patulous. Inner lip oblique, very slightly concave; 

 on the body it is formed by a large porcellanous white pad pro- 

 jecting in a rounded knob, between which and the sharp edge of 

 the outer lip is a small shallow depression ; retreating and becoming 

 thinner on the body, this pad projects prominently across the 

 shell above the umbilicus, which it somewhat covers, but a fur- 

 row above the umbilical pillar cuts in on it ; it spreads out in a 

 half-circle on the point of this umbilical pillar ; below this point 

 another umbilical furrow cuts still deeper into it, but toward the 

 point of the pillar it is broadened and reverted on the thickening 

 of the slight circumumbilical carination. Umbilicus strong and 



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