10 EHIZOPODA. 



1. Monostega. — Body consisting of a single seo"- 



ment : shell of one chamber. 



2. Stichostega. — Body composed of segments dis- 



posed in a single line : shell consisting of a 

 linear series of chambers. 



3. Helicostega. — Body consisting of a spiral series 



of segments ; shell made up of a number of 

 convolutions. 



4. Entomostega. — Body consisting of alternate 



segments spirally arranged: shell chambers 

 disposed on two alternating axes forming a 

 spiral. 



5. Enallostega. — Body composed of alternate 



segments not forming a spiral : chambers ar- 

 ranged on two or three axes which do not 

 form a spiral. 



6. Agathistega. — Body consisting of segments 



wound round an axis : chambers arranged in 

 a similar manner, each investing half the 

 entire circumference. 



All these orders, with the exception of the first, 

 are sometimes designated by the collective appel- 

 lation of ' Polythalamia.^ 



A somewhat different arrangement has been 

 adopted by Schultze, who divides the Polythala- 

 inia into three sections, viz. : — 



1. Helicoidea, including those forms in which 



the scAT^eral chambers of the shell are ar- 

 ranged in a convolute series : 



2. Rhahdoidea, in which they are placed in a 



direct line : and, 



3. SoToidea, where they are disposed in an irre- 



gular manner. {Vide Table, p. 11.) 



