1380 THE VOYAGE OF H.M.S. CHALLENGER. 



smooth, with regular, circular pores. Abdomen truncate, conical, with sixteen to twenty-four 

 divergent ribs, which are straight or slightly curved, and connected by from four to six transverse, 

 circular rings. The large regular meshes, so produced, form sixteen to twenty-four longitudinal 

 series, and are rounded in the upper, square in the lower transverse rows. 



Dimensions. Length of the three joints, a 0'02, b 0'06, c 0'09; breadth, a 0'03, b 0'08, c 014. 



Habitat. Fossil in Barbados. 



13. Cycladophora favosa, n. sp. (PL 62, figs. 5, 6). 



Shell dome-shaped, without collar stricture, but with a deep lumbar stricture. Cephalis flat, 

 cap-shaped, without horn, or with a rudimentary conical horn, with small circular pores. Length 

 of the three joints = 1:4:3, breadth = 2:5:4. Thorax subspherical, rough, with regular, circular, 

 hexagonally-framed pores. Abdomen truncate, conical, with eighteen to twenty-four prominent 

 ribs ; between every two ribs only two or three ovate pores occur. Mouth circular, with eighteen 

 to twenty -four teeth. The shape of the abdomen is rather variable (figs. 5, 6). 



Dimensions. Length of the three joints, a 0'02, b O08, c O06 ; breadth, a 0"04, b O09, c 0'07. 



Habitat. Western Tropical Pacific, Station 225, depth 4475 fathoms. 



Subgenus 5. Cyclamptidium, Haeckel. 



Definition. Abdomen nearly cylindrical or prismatic, with numerous (ten to 

 twenty or more) straight, vertical, parallel ribs. Mouth wide open, truncate. 



14. Cycladophora fenestrata, n. sp. (PL 68, fig. 2). 



Shell rough, with two slight strictures. Length of the three joints = 1:5:5, breadth = 1:6:5. 

 Cephalis conical, with a conical, dimpled horn of twice the length. Thorax nearly spherical, with 

 regular, circular pores, and small conical spines. Abdomen cylindrical, with eighteen stout, 

 parallel, vertical ribs, which are connected by six to eight horizontal, circular rings ; therefore 

 regular transverse and longitudinal rows of square or circular pores occur. Mouth truncate, 

 circular. 



Dimensions. Length of the three joints, a 0'02, b 01, c 01 ; breadth, a 0'03, b 012, c 01. 



Habitat. Central Pacific, Station 265, depth 2900 fathoms. 



15. Cycladophora stiligera, Ehrenberg. 



Cycladophora stiligera, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 68, Taf. xviii. 

 fig. 3. 



Shell smooth, with two distinct strictures. Length of the three joints = 2 : 7 : 8, breadth = 

 2:9:7. Cephalis subspherical, with a conical horn of twice the length. Thorax subspherical, 

 smooth, with regular, circular pores. Abdomen cylindrical, with twelve parallel, vertical ribs, which 



