MOLLTJSOA OF THE * CHALLENGEE ' EXPEDITION. 409 



H. 1-4. B.0-53. Penultimate whorl, height 0-2, Mouth, height 

 0-85, breadth 03. 



This is a peculiarly beautiful species, singular in the breadth of 

 its form, but very much more in the extreme regularity of its 

 biconically fusiform shape. It recalls in an extraordinary way 

 Conns dormitor, Solander, an Eocene fossil from the Barton beds 

 of the Hampshire basin, and the cone-like Pleurotomas of that 

 formation, such as P. prisca, Sol., P. amphiconus, Sow., P. co- 

 no'ides, Sol., and P. biconus, Edwds. Dr. H. Woodward says it is 

 near P. ventricosa, Lam. ix. p. 372, a Grignon fossil, with which 

 I have not had an opportunity of comparing it during the 

 transfer of the Geological collections from the British Museum 

 to Kensington. 



16. Pletjeotoma (Deillia) pteeha, n. sp. (jrvppos, tawny.) 



St. 233 a. May 16-19, 1875. Lat. 34° 35' N., long. 135° 10' E. 

 Kobi, Japan. 8-50 fms. Mud. 



Shell. — High, narrow, conical, with a longish, somewhat con- 

 tracted, conical base running out into a largish snout, obliquely 

 ribbed, and covered with spiral threads ; the suture is slightly 

 constricted. Sculpture. Longitudinals — there are on the last 

 whorl thirteen, on the first regular whorl eight, oblique, rounded 

 ribs, which are obsolete at the top of the whorls, extend to the 

 lower suture, but die out on the base ; they are parted by 

 shallow rounded furrows, rather wider than they are : the lines 

 of growth are harsh and numerous. Spirals — at the top of each 

 whorl is a slight swelling, carrying two stronger and many 

 feebler flat spiral threads. The sinus-area is scored by fine, 

 but irregular, spiral threads. The whole of the rest of the sur- 

 face is covered by rounded spiral threads, which are alternately 

 stronger and finer. On the snout the finer ones disappear, and 

 the stronger ones become sparser ; the three highest of the 

 stronger ones rise into slight knots on the ribs. Besides all 

 these, the whole surface is delicately and regularly scratched 

 microscopically. Colour porcellanous white, very much stained 

 in the interstices of the ribs, and especially on the larger spiral 

 threads, with tawny or light chestnut-colour, which is also seen 

 on the point of the pillar and canal. Spire high and conical, its 

 profile-lines somewhat broken by the angular prominence of 

 the ribs and by the rounded constriction of the suture. Apex 

 broken . Whorls 10 (remaining), of regular rather rapid increase, 

 short, contracted above, expanding below, angulated by the pro- 



