DIAPHOEOPODON MOBILE. 125 



retracted and he never saw them formed a second time ; 

 they have not been noticed by subsequent observers. 

 The pseudopodia are usually attenuate, and are radiat- 

 ing, and simple or forked. 



Genus 44. CLYPEOLINA Penard, 1901. 

 Clypeolina Pbnaed in Rev. Suisse Zool. IX (1901), p. 237. 



Test ovoid, compressed, formed of a double envelope ; 

 the outer covering consisting of two separate chitinous 

 valves covered with small scales and silicious particles ; 

 the inner covering consisting of a membranous sac ; 

 pseudopodia long, filose, frequently branched. 



Penard formed this genus to receive a species 

 similar to a Pseudodiffiugia but having a well-developed 

 keel around the margin of the test ; this keel is formed 

 by the junction of the flattened edges of the two half 

 outer valves forming the test, and it may be slight or 

 even altogether absent. The generic and constant 

 characteristic feature of G. marginata is this bivalve 

 test possessed by no other known testaceous Phizopod. 

 The separate inner membrane and method of division 

 are also peculiar features. 



The only known member of the genus, G. marginata, 

 has in Grreat Britain been recorded from a single 

 locality only ; no doubt it will be found elsewhere if 

 diligently looked for, but unless carefully examined it 

 is apt to be mistaken for a Pseudodifflugia. Like 

 many species belonging to allied genera it may occur 

 in a very limited habitat, i. e. a single small pool or 

 ditch in a marsh or a single tussock of sphagnum may 

 contain numerous individuals of a particular species 

 whilst in adjoining and similar situations none are to 

 be found; it is also by no means certain that they 

 will be found in the same places during successive 

 years. 



