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



Dimensions. — Length of the cortical shell (or principal axis) O'lo, breadth of it (or transverse 

 axis) O'l, height of it (or sagittal axis) 0'07 ; pores O'OOG, bars O^OOS ; medullary shell (diameter) 

 0-03. 



Habitat. — Pacific, central area, Station 271, depth 2425 fathoms. 



2. Larnacilla j^rometor, n. np. 



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

 the bars ; about ten an 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. Medullajy 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 Ol, height 0-05 ; pores 0-015, bars 

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



Habitat. — Indian Ocean, Zanzibar, PuHen, depth 2200 fathoms. 



3. Larnacilla subglohosa, 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 : 1-4 : 1-5. Internal four gates ellijjtical, 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 sheU 0-15, breadth O'li, height 0-13 ; pores 0006 to 0-012, 

 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 ou 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 bai-s about 

 0-004 ; medullary sheU 0-013. 



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



Genus 273. Larnacidium,^ n. gen. 



Definition. — Lam ac id a with a simple lentelliptical cortical shell, connected by 

 the lateral wings of a latticed transverse gu'dle with the simple, spherical or 

 lentelliptical, medullary sliell. Surface armed with radial spines. 



' iarnacidium = Little cbest, diminutive oi Larnax ; T^xpi/a^. 



