290 CLASS V. CEPHALOPODA. ORDER I. POLYTHALAMIA. 
Pl. CCXCVII. Fig 5. 
Sprrotocutina WesBIANA, Nobis. 
Triloculina Webbiana, D’Orbigny, Mollusques des Hes Canaries, Forami- 
niferes, pl. 3. f. 13 to 15. 
Pl. CCXCVII. Fig. 6. 
SprroLocu.Lina Bertrueroriana, Nobis. 
Quinqueloculina Berthelotiana, D’Orbigny, Mollusques des Iles Canaries, 
Foraminiferes, pl. 3. f. 25 to 27. 
POLYSTOMELLA, Lamarck. 
Testa discoidea, subturbinata, spira szepissimeé regulari, plus minusve 
prominula ; anfractibus contiguis, loculis irregulariter divisis. 
The Polystomelle are for the most part distinguished as having a 
somewhat nautiloid construction, but their infinite variation of form ren- 
ders it exceedingly difficult to fix a proper generic uniformity of charac- 
ter. The mere structure and formation of these bodies is all that can be 
at present resorted to as a means of classification ; and the very anoma- 
lous and extraordinary shapes which they present defy the ingenuity of 
the most skilful systematists. The family of Les Helicosteques, which we 
include under this genus, is by far the largest which D’Orbigny insti- 
tuted: he divides it into three sections, and these are again subdivided 
into no less than twenty-six genera. ‘The first section, Les Turbinoides, 
contains ten genera, as follows: Clavulina, Uviferina, Bulimina, Valvulina, 
Rosalina, Rotalia, Calcarina, Globigerina, Gyroidina and Truncatulina ; 
the second section, Les Ammonoides, contains four only: Planulina, Pla- 
norbulina, Operculina and Soldania ; and the last section is divided into 
twelve genera: Cassidulina, Anomalina*, Vertebralina, Polystomella, Den- 
* A most appropriate title, if it has reference to anomaly of structure. 
