1472 THE VOYAGE OF H.M.S. CHALLENGER. 



11. Lithostrobus conulus, n. sp. (PI. 80, fig. l). 



Shell slenderly conical, smooth, with straight axis, and seven to ten distinct strictures. Joints of 

 different lengths ; the fourth and fifth about twice as long as the preceding and following joints, the 

 former with four to five, the latter with two to three transverse rows of large irregular pores ; the 

 seventh joint twice as broad as the third. Horn of the cephalis short, pyramidal. 



Dimensions. Length of the shell (with eight joints) 014, length of the fifth joint 0'03 ; 

 breadth 0'06. 



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



12. Lithostrobus picus, Biitschli. 



Lithostrobus picus, Biitschli, 1882, Zeitschr. f. wiss. ZooL, vol. xxxvi. p. 529. 

 Euc,yrtidium picus, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 72, Taf. xi. 

 fig. 1. 



Shell slenderly conical, smooth, with straight axis, and six to eight slight strictures. Joints of 

 different lengths, the second twice as long as each of the three following, and four times as long as 

 each of the last joints; the sixth joint one and a-half times as broad as the second. Small circular 

 pores in regular transverse rows; six rows in the first and the second, three rows in the third, fourth, 

 and fifth, a single row in each of the last joints. Horn of the cephalis cylindrical, half as long as 

 the shell. 



Dimensions. Length of the shell (with eight joints) 012, length of the second joint 0'03 ; 

 breadth 0'04. 



Habitat. Fossil in Barbados. 



13. Lithostrobus argus, Biitschli. 



Lithostrobus argus, Biitschli, 1882, Zeitschr. f. wiss. Zool., vol. xxxvi p. 529. 



Eucyrtidium argus, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 70, Taf. ix. fig. 1. 



Shell conical, thorny, with straight axis, and five to seven slight strictures. Joints of different 

 lengths, each of the three first twice as long as each of the following. Pores large, roundish, in trans- 

 verse rows ; three rows in the first and the second joints (which in the figure of Ehrenberg are not 

 separated), two rows in the third joint, a single row in each of the following joints. Horn of the 

 cephalis large, conical, curved, half as long as the shell. 



Dimensions. Length of the shell (with seven joints) 0'2, length of the fourth joint (and each 

 following) 0-02 ; breadth 01. 



Habitat. Fossil in Barbados. 



14. Lithostrobus acuminatus, Haeckel. 



Eucyrtidium acuminatum, Bury, 1862, Polycystins of Barbados, pi. i. fig- 1- 



Shell slenderly conical, smooth, with straight axis, and four to six deep strictures. Joints gradu- 

 ally increasing in length. Pores in regular, transverse rows, commonly three rows in the first, four 



