854 THE VOYAGE OF H.M.S. CHALLENGEE. 



Subgenus 2. Phractopeltidium, Haeckel. 



Definition. — Outer shell composed of twenty united plates, the sutures of their 

 meeting condyles being grown together. 



8. Pliractopelta aspidomma, n. sj). 



Outer shell composed of twenty united plates, the meeting condyles of which are grown together. 

 ■On the base of each radial spine (where its outer free part ajises from the surface of the outer 

 shell), two large elliptical aspinal pores, two to four times as large as the other roundish pores. 

 Eadial spines compressed, sword-shaped, about as long as the radius of the shell. 



Dimensions. — Diameter of the outer shell 01, of the inner 0'05. 



Hahitat. — Equatorial Atlantic, Station 347, surface. 



9. Pliractopelta haliomma, n. sp. 



Outer shell composed of twenty united p»lates, the meeting condyles of which are grown together. 

 On the base of each radial spine two large kidney-shaped aspinal pores, little larger than the other 

 irregular pores. Radial spines compressed, linear, two-edged, much longer than the diameter of the 

 shell. 



Dimensions. — Diameter of the outer shell 0'09, of the inner O'Oo. 



Hahifat. — South Pacific, Station 295, surface. 



10. Phractopelta tessaromma, Haeckel. 



Outer shell composed of twenty united plates, the meeting condyles of which are grown together. 

 On the base of each radial spine four crossed egg-shaped aspinal pores, two opposite of which are 

 much larger than the two others. Sutural pores UTegular. Eadial spines cyhndrical or little com- 

 pressed, thin, longer than the diameter of the shell. 



Dimensions. — Diameter of the outer shell O'l, of the inner 0'04. 



Hahitat. — Central Pacific, Station 266, surface. 



II. Pliractopelta hystrix, HaeckeL 



Haliomma hystrix, J. Miiller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 37, Taf. v. 



figs. 1, 2. 

 Aspidomma hijstrix, Haeckel, 1862, Monogr. d. Piadiol., p. 424. 



Outer shell composed of twenty united plates, the meeting condyles of which are grown together. 

 On the base of each radial spine four crossed circular aspinal spines of equal size. Sutural pores 

 roundish, of about the same size. Eadial spines conical, about as long as the radius of the shell. 



Dimensions. — Diameter of the outer shell 0-07, of the inner 0'024. 



Habitat. — Mediter 'anean (Nice), J. Miiller, surface. 



