MUSEUM OF COMPARATIVE ZOOLOGY. 377 



sides approach each other and bound a median furrow, coarsely transversely 

 ridged (as in Pleurotomaria), which extends to the end of the foot. 



The mantle-edge is smooth or very sparsely papillate, slightly thickened. 

 The free end of the intestine projects on the right side over the neck, with its 

 termination constricted by a sphincter, and then expanded into a cup-shaped 

 circular foramen. On the left side is the gill, consisting of a central somewhat 

 muscular ensiform basement, from which depend two sets of elongate-triangu- 

 lar lamellae separated by a narrow ridge. The left-hand set are slightly the 

 longer. Most of the gill is free. Its distal end is pointed, and the lamellae 

 hang, side by side, with the ridge between the two series, as in Nucula. The 

 intestine takes a curve to the left side, where the renal gland is visible between 

 it and the gill. I observed no osphradium. 



The mouth is small. A short distance behind it is a deep radular diverticu- 

 lum. The jaws are small, triangular, and dark brown. The gullet opens 

 almost directly into an elongate large longitudinally wrinkled stomach. Be- 

 hind it the very large intestine, with longitudinally striated walls, extends 

 backward about half a whorl ; then turns upward and forward for a third of 

 a whorl; then back again upon itself about Jhe same distance; then forward to 

 its anal termination above described. 



The liver and seminal gland appear to resemble those of ordinary Trochids. 



The operculum is amber-colored, polished, thin, and centrally depressed. 

 It has about a dozen whorls. The opercular pad is ovoid and rather small. 



The radula is quite small and the anterior part dark brown. The intestine 

 in all the specimens is crammed with a greenish mud consisting of disinte- 

 grated foraminifera. 



The dentition recalls that of Calliostoma, Solariella, Margarita, etc., and 

 presents nothing very characteristic. 



The central tooth has a broad thin base, subrectangular, and a little wider at 

 the anterior corners. The stem of the cusp and the cusp are narrow. The 

 latter is simple, rather small, short and recurved. It is not denticulate. There 

 are three or four admedian or lateral teeth, rather long, with small bases, rather 

 broad simple moderately curved brownish cusps. There are about twenty- 

 five uncini, half of which spring from lozenge-shaped bases looking like a 

 pavement, are long, narrow, slender, moderately curved with spatuliform tips. 

 One edge of these tips is microscopically serrate, and below the serrate part on 

 the same side is a single larger denticle, standing out like a short thumb. 



The external uncini are thin, flat, wide, and hardly curved. Their distal 

 ends are flat and broad, with the edge simple and entire. These teeth gradu- 

 ally diminish in size and width, as usual in Trochidce. The formula woulc' 

 be 25 -+- 3 -f- \ + 3 + 25, or very nearly that, but time has been wanting in 

 wliich to undertake the laborious task of an exact enumeration of these minute 

 and tangled objects, of wliich the general features have just been recorded. 



All the specimens of l^urcicula previously obtained were incomplete and 

 deprived of epidermis. The Pacific species, which will be described in the 

 Report on the Voyage of the Albatross, reaches a large size (50.0 mm. high by 



