1502 THE VOYAGE OF H.M.S. CHALLENGER. 



The genus Lithocampe is the oldest of all " Polycystina," being founded by Ehren- 

 berg in 1838 upon Lithocampe radicula. Afterwards numerous other species, which 

 belong to very different genera, were described by him. In 1862 I attempted to give 

 a more strict definition of this genus in my Monograph (p. 312 to 315), and separated 

 it from the closely allied and often confounded Eucyrtidium by the absence of a 

 cephalic horn. The great number of species afterwards discovered leads to the stricter 

 definition given above. 



Subgenus 1. Lithocampula, Haeckel. 



Definition. All joints of the shell (except often the first) are equal or nearly 

 equal in length. 



1. Lithocampe eupora, Haeckel. 



Eucyrtidium euporum, Ehrenberg, 1872, Abhandl. d. k. Akacl. d. Wiss. Berlin, p. 291, Taf. iv. iig. 30. 



Shell smooth, ovate or subconical, with three deep strictures. Four joints equal in length, 

 gradually increasing in breadth, each with three transverse rows of regular, circular, hexagonally- 

 framed pores ; the fourth joint is the broadest. Mouth little constricted, of the same breadth as 

 the third joint. 



Dimensions. Length of the shell (with four joints) 0'08 ; length of each joint 0'02, greatest 

 breadth 0'06. 



Habitat. Tropical Atlantic, Station 348, depth 2450 fathoms; North Atlantic, depth 3600 

 fathoms (Morse). 



2. Lithocampe platycephala, Haeckel. 



Eucyrtidium platycephalum, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, pp. 145, 

 293, Taf. iii. fig. 16. 



Shell smooth, subconical or slenderly ovate, with three slight strictures. Four joints equal in 

 length, slightly increasing in breadth towards the mouth. The hemispherical cephalis with longi- 

 tudinal ribs and irregular pores, each of the three other joints with four transverse rows of regular, 

 circular pores. Mouth strongly constricted, half as broad as the third and fourth joints. 



Dimensions. Length of the shell (with four joints) 012 ; length of each joint O'OS, greatest 

 breadth 0'06. 



Habitat. North Atlantic, depth 3600 fathoms (Morse). 



3. Lithocampe nereidum, Haeckel. 



Lithocampe nereidum, Haeckel, 1862, Monogr. d. Eadiol., p. 319. 



Eucyrtidium nereidum, Ehrenberg, 1854, Monatsber. d. k. preuss. Akad. d. "Wiss. Berlin, p. 242 ; 

 Mikrogeol., Taf. xxxv. B, 6, fig. 22. 



Shell smooth, slenderly ovate, with four deep strictures. Five joints equal in length, the fourth 

 being the broadest. Each joint with three transverse rows of small, regular, circular pores (some- 



