460 KEY. R. BOOG WATSON ON THE 



body to the canal, from which point it is drawn out rather straight ; 

 its edge advances in the middle very prominently ; above this it 

 forms a high shoulder, between which and the body-whorl lies 

 the deep, rounded, and very wide-mouthed sinus ; towards the 

 front of the mouth the edge rims straight, then retreats, so as to 

 form a broad, slight, small sinus at the top of the canal, and then 

 runs straight. Inner lip : there is a thin glaze excavated slightly 

 in the substance of the shell. The pillar is long, narrow, and 

 fine-pointed, with a slight swelling coiling round its base, where 

 its junction with the body is but slightly concave. H. - 85. 

 B. 6-35. Penultimate whorl, height 0-16. Mouth, height 0-43, 

 breadth 0'2. 



This species has a considerable likeness to P. torquatum, Phil. ; 

 but that is a larger, broader, stumpier form, has the individual 

 whorls shorter, more strongly keeled, ornamented with little 

 rounded tubercles instead of with narrow, pinched-up, very oblique 

 riblets ; has also a much more horizontal suture ; the whorls, too, 

 are not cylindrical, but contract from the keel to the lower suture ; 

 the base is much more drawn in, and the pillar much shorter ; 

 the whole texture also and sculpture is much stronger than in 

 the ' Challenger ' species. 



The specimens from St. 24 and St. 85 are markedly stumpier 

 in form, more sharply keeled, and with a higher shoulder and 

 a rather smaller embryonic apex ; but the whole details of sculp- 

 ture are identical. 



53. Plettrotoma (Deerancia) pachia, n. sp. (ttclxvs, fat.) 

 St. 24. March 25, 1873.' Lat. 18° 38' 30" N., long. 65° 5' 30" ~W. 

 North of Culebra Island, St. Thomas, Dan. West Indies. 390 fms. 

 Coral-mud. 



Shell. — Ovate, white, smooth, of rounded outlines, with a rather 

 high, small, and sharp-pointed apex, a swoln body-whorl, and a 

 rounded base produced into a small, broad, one-sided snout. 

 Sculpture. Longitudinals — there are only very fine hair-like lines 

 of growth, of which here and there at regular intervals one 

 becomes much more strongly marked than the others. Spirals — 

 the whole surface is sparsely scored with very shallow, scratched- 

 out, narrow furrows, parted by flat intervals of from two to six 

 times their breadth ; in the sinus-area they are a little closer 

 than elsewhere ; on the snout they gradually broaden till their 



