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



5. Prunulum crenatum, Haeckel. 



1 Haliomma crenatum, Elirenberg, 1854, Mikrogeol., Taf. xxii. fig. 36. 

 Actinomma crenatum, Stblir, 1880, Palseontogr., vol. xxvi. p. 94, Taf. iii. fig. 3. 

 Caryolithis crenata, Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 43. 



Cortical shell thick walled, slightly rough or thorny, with small, regular, circular pores, of the 

 same breadth as the bars ; sixteen to eighteen on the half equator. Proportion of the two axes = 

 4 : 3. Both medullary shells ellipsoidal. (The figure of Stohr represents exactly the fossil form, 

 as I have observed it myself in the Caltanisetta rocks, whilst the figure of Ehrenberg is inaccurate 

 and doubtful. The same form, somewhat variable in size and in the number of the pores, I have 

 also observed in the Pacific ooze.) 



.Dimensions. Major axis 0'14 to 0'17, minor O'l to 0'13 ; pores and bars O'OOG ; main axes of 

 the medullary shells 0'09 and 0'03. 



Habitat. Fossil in the Tertiary rocks of Sicily (Grotte and Caltanisetta) ; living in the Central 

 Pacific, Station 268, depth 2900 fathoms. 



6. Prunulum triplex, Haeckel. 



Haliomma triplex, Ehrenberg, 1854, Microgeol., Taf. XXXVB. fig. LSiv., q. 

 Actinomma triplex, Haeckel, 1862, Monogr. d. liadiol., p. 444. 



Cortical shell thin walled, covered with numerous very thin, short, bristle-like spines. Pores 

 small, regular, circular, of the same breadth as the bars ; fourteen to sixteen on the half equator. 

 Proportion of the two axes = 3:2. Both medullary shells ellipsoidal. The description of 

 Ehrenberg as is very often the case- is quite incongruent with his figure. From a combination 

 of both I give here the diagnosis of a deep-sea species, which is possibly identical with it. 

 The velvet-like covering of very short and thin bristles is peculiarly characteristic of this species. 



Dimensions. Major axis 01, minor 0'65 ; pores and bars 0'004 ; main axes of the medullary 

 shells 0-04 and 0'02. 



Habitat. North Atlantic, 1800 fathoms, Ehrenberg ; Station 353, depth 2965 fathoms. 



Subgenus 2. Prunulissa, Haeckel. 



Definition. Network of the cortical shell irregular, with meshes of different form 

 or size (usually roundish, but sometimes lobed or compound). 



7. Prunulum persicum, n. sp. 



Cortical shell thick walled, with smooth surface and irregular, roundish, double-contoured pmvs, 

 twice to four times as broad as the bars ; eight to ten on the half equator. Some of the pores 

 are simple, often subcircular, others lobed, i.e., composed of from two to three confluent pores as 

 in Am/phitphcera pluto (PI. 17, figs. 7). Proportion of the two axes = 3:2. Both medullary shells 

 ellipsoidal (or the inner spherical). 



