1470 THE VOYAGE OF H.M.S. CHALLENGER. 



4. Lithostrobus tetrastichus, n. sp. (PI. 80, fig. 6). 



Shell slenderly conical, smooth, with straight axis and six to eight deep strictures. All joints 

 nearly of the same length, the eighth joint twice as broad as the second. In each joint four trans- 

 verse rows of regular, circular pores with very thin bars. Horn of the cephalis conical, strong, 

 curved, about as long as two joints. 



Dimensions. Length of the shell (with eight joints) 012, of each joint 0'015 ; breadth of the 

 second joint 0'02, of the eighth 0'04. 



Habitat. Central Pacific, Station 272, depth 2600 fathoms. 



5. Lithostrobus pentastichus, n. sp. 



Shell slenderly conical, smooth, with straight axis, and six to eight slight strictures. All joints 

 nearly of the same length, the sixth twice as broad as the third. In each joint five transverse 

 rows of small circular pores. Horn of the cephalis pyramidal, of twice the length. (Similar to 

 Eucyrtidium cienkowskii, PL 80, fig. 9, but regularly conical, with all the joints equal in length.) 



Dimensions. Length of the shell (with eight joints) 0'2, of each joint 0'025 ; breadth of the 

 third joint 0'04, of the sixth 0'08. 



Habitat. South Pacific, Station 298, depth 2225 fathoms. 



6. Lithostrobus hexastichus, n. sp. (PL 80, fig. 15). 



Shell campanulate-conical, smooth, with straight axis, and six to eight slight strictures. All 

 joints nearly of the same length, the sixth joint twice as broad as the second. In each joint six 

 transverse rows of subregular, hexagonal pores, with thin bars. Horn of the cephalis conical, 

 straight, of about the same length. (The specimen figured is a somewhat irregular one ; other 

 specimens found afterwards were perfectly conical and regular, with joints of equal length). 



Dimensions. Length of the shell (with six joints) 0'16, of each joint 0'027. 



Habitat. Central Pacific, Station 270 to 274, depth 2350 to 2925 fathoms. 



Subgenus 2. Cornustrobus, Haeckel. 



Definition. Shell horn-shaped, conical, with curved axis ; all joints nearly equal in 

 length, gradually increasing in breadth. 



7. Lithostrobus cyrtoceras, n. sp. (PL 80, fig. 2). 



Shell horn-shaped, conical, with curved axis, smooth, with six to eight deep strictures. All 

 joints nearly of the same length, gradually increasing in breadth ; the sixth joint twice as broad as 

 the second. In each joitft about four transverse series of regular circular pores. Horn of the 

 cephalis conical, slightly curved, of the same length. 



