THE LOBOSA 



89 



aperture^ being closed again when the pseudopodia are withdrawn. 

 Cochliopodium, Hert. and Less., then, is the connecting-link between the 

 two orders. In Corycia, Dujardin, the test is supple and membranous, but 

 the pylome remains open. In Pseudochlamys, Clap, and Lach., the shell is 

 shaped like that of a limpet, but is very flexible, and the margin of the 

 pylome may in the retracted condition be inflected to form a shelf like 

 the velum of a medusa. In 

 Parmulina, Penard, the test is 

 in the shape of a cup or bowl. 

 In Hyalosphenia, Stein, the test 

 is rigid except at its margin. 



Family DIFFLUGIIDAE. 

 Tests usually globular, or flask- 

 ehaped with a narrow pylome. 

 Outer sheath of the test with 

 hard plates, or with adherent 

 foreign particles, or with both. 



Difflugia, Leclerc, is a genus 

 which exhibits a great many 

 varieties of form, some of which 

 Are very common. The shell 

 is usually flask -shaped, and 

 -consists of a tough double 

 membrane to which various 

 foreign bodies, such as diatom 

 shells, sponge spicules, sand- 

 grains, etc., are cemented. The 

 pseudopodia are rarely more 

 than two or three in number, 

 .digitiform and blunt, but some- 

 times frayed at the extremities. 

 Some of the larger varieties are 

 over 0*5 mm. in length. 



Centropyxis, Stein ( = Echi- 

 nopyxis, Clap, and Lach.), is 



related to Dijftugia, but the \j FIG. 20. 



Shell is usually discoidal or A) rjiffi^ia pyrtformis, Perty, with very large 

 oval, with the pylome excentric diatom shells attached to the theca. B, test of 

 ... A T , Quadrula symmetrica, Wallich. C, Lecqiiereusia 



in position. It 18 covered spiralis, Ehr. D, diagram of test of Pontigulasia 

 irrpcrnlarlv witli fnrpirrn -nor- incisa, Rhumbler, showing the collar (co) and bridge 



.reguiariy witn loreign par- (b) E> viewof the bridg (6) of Poil/ ^ u ^ a from 



tides, and sometimes exhibits above. (A-C after Leidy; I), E after Penard.) 

 two or three short spines. 



Pontigulasia, Rhumbler, and -Cucurbitella, Penard, are distinguished 

 by the presence of a short collarette round the pylome. In Pontigulasia 

 <Fig. 20, D and E) a broad flat bridge runs across the base of this collarette 

 and divides the pylome into two apertures. In Lecquereusia, Schlumberger 

 (Fig. 20, C), the shell is cornuate or slightly spirally twisted. The genera 

 Quadrula, Nebela, and Heleopera form shells with siliceous plates and are 

 not usually decorated at all with foreign particles. Quadrula, F. E. 



