604 



THE VOYAGE OF H.M.S. CHALLENGER. 



aggregated without any order, like the Acervulinida among the Foraminifera. In some 

 eases also here the primordial chamber is a trizonal Larnacilla-shell, in other cases it is a 

 simple, subspherical or lentelliptical shell. 



The last family, the Phorticida, is formed of irregular L a r c o i d e a, in which a 

 lentelliptical trizonal Larnacilla-she]\ (as an inner medullary shell) is enveloped by an 

 irregular, latticed, or spongy cortical shell. They can be regarded as abnormalities or 

 irregular deformities of Larnacida or Pylonida. 



The central capsule of the Larcoidea is originally lentelliptical and preserves this 

 form, the " triaxial ellipsoid," in the greater number of genera. In some groups it follows 

 the prevalent growth of the shell in the direction of one of the three dimensive axes, 

 and becomes prolonged in this way. In many chambered forms (particularly Tholonida 

 and Zonarida) the growing central capsule gets constricted, corresponding to the con- 

 strictions of the shell. In the Soreumida and Phorticida its form often becomes irregular. 

 But in general for the greater number of Larcoidea the lentelliptical form of their 

 central capsule is quite characteristic. 



Synopsis of the Families of Larcoidea. 



Cortical shell completely 

 latticed, without external 

 gates (or interzonal fissures), 

 without annular constric- 

 tions and domes. 



Larcoidea with a regu- 

 lar or symmetrical shell, 

 the growth of which is 

 determined by the three -j 

 dimensive axes. (Both 

 poles of each axis are 

 equal.) 



Medullary shell absent or 

 simple (spherical or lent- 

 elliptical), 



Medullary shell trizonal or 

 Larri(iciHa-s\\a.ped (com- 

 posed of three dirneiisive 

 girdles), 



Cortical shell incompletely latticed, with two to four or 

 more symmetrically disposed gates or fissures remaining 

 between latticed dimeusive girdles, 



Cortical shell completely 

 latticed, without external 

 gates (or interzonal fissures), 

 with two to four or more an- 

 nular constrictions, which 

 separate three to six or 

 more dome-shaped pro- 

 tuberances. 



Constrictions of the cortical 

 shell in diagonal planes; 

 domes in dimensive axes, 



Constrictions of the cortical 

 shell in dimensive planes ; 

 domes in diagonal axes, 



Larcoidea with a sym- 

 metrical or irregular 

 shell, either with spiral 

 growth or with quite 

 irregular growth. (Both 

 poles of one axis are 

 different.) 



Cortical shell 

 growth. 



with 



f Spiral cortical shell bilateral 



(with plane spiral), 

 spiral J 



] Spiral cortical shell asym- 

 metrical (with ascending 



[ spiral), . 



Cortical shell with 

 irregular growth. 



quite 



Cortical shell simple, with 

 one single chamber, 



Cortical shell composed of 

 a number of heaped up 

 or aggregated chambers, 



1. LARCARIDA. 



2. LARNACIDA. 



3. PYLONIDA. 



4. THOLONIDA. 



5. ZONARIDA. 



6. LITHELIDA. 



7. STREIJLEMIDA. 



8. PHORTICIDA. 



9. SOREUMIDA. 



