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



Dimensions. Length of the cortical shell (or principal axis) 013, breadth of it (or transverse 

 axis) 01, height of it (or sagittal axis) 0'07 ; pores 0'006, bars 0'003 ; medullary shell (diameter) 



0-03. 







Habitat. Pacific, central area, Station 2*71, depth 2425 fathoms. 



2. Larnacilla prometor, n. sp. 



Cortical shell with rough surface and regular network ; pores three times as broad as 

 the bars ; about ten on the half meridian, eight on the half equator. Proportion of the three 

 axes = 1:2:3. Internal four gates (between transverse and lateral girdles) kidney-shaped, twice as 

 broad as high. Medullary shell lentelliptical, of the same form as the external cortical shell, but 

 only one-third as large. 



Dimensions. Length of the cortical shell 015, breadth 01, height 0'05 ; pores 0'015, bars 

 0-005 ; medullary shell 0'02 to 0'05. 



Habitat. Indian Ocean, Zanzibar, Pullen, depth 2200 fathoms. 



3. Larnacilla subglobosa, n. sp. 



Cortical shell nearly spherical, with thorny surface and irregular network ; pores roundish, 

 twice to four times as broad as the bars; twelve to sixteen in the half circumference. Proportion of 

 the three axes very little different = 1 '3 : 14 : 1 '5. Internal four gates elliptical, one and a half 

 times as broad as high. Medullary shell spherical, one-fourth as broad as the cortical shell. 



Dimensions. Length of the cortical shell 015, breadth 014, height 013; pores O'OOG to - 012,. 

 bars 0-003 ; medullary shell 0'035. 



Habitat. Pacific, central area, Station 266, depth 2750 fathoms. 



4. Larnacilla medullaris, n. sp. 



Cortical shell lentelliptical, with smooth surface and irregular network ; pores roundish, very 

 small, scarcely as broad as the bars ; about eight to nine on the half meridian, six to seven on the 

 half equator. Proportion of the three axes = 3:4:6. Internal four gates elliptical. Medullary 

 shell spherical, scarcely one-third as broad as the cortical shell. (This small species may be only 

 the medullary shell of some other Larcoid, the cortical shell of which is not yet formed.) 



Dimensions. Length of the cortical shell 0'06, breadth 0'04, height 0'03 ; pores and bars about 

 0-004 ; medullary shell (M)13. 



Habitat. Pacific, central area, Station 265, depth 2900 fathoms. 



Genus 273. Larnacidium? n. gen. 



Definition. L arnacida with a simple lentelliptical cortical shell, connected by 

 the lateral wings of a latticed transverse girdle with the simple, spherical or 

 leutelliptical, medullary shell. Surface armed with radial spines. 



1 Larnacidium = Little chest, diminutive of Larnax; Ao>J. 



