8 BKITISH FRESHWATER EH1ZOPODA. 



Although this species is now almost universally 

 called Difflugia pijriformis, Ehrenberg's name has the 

 priority and must be adopted in accordance with the 

 rules of zoological nomenclature. While there can 

 moreover be no question as to the species being 

 Ehrenberg's Difflugia oblonga, its identity with the 

 pyrifonnis of Perty admits of doubt ; indeed from its 

 smooth outline, slender neck, and nearly regular mark- 

 ings, Perty's figure may represent a Nebda. [From 

 the description, however " Schale birnformig, man- 

 chmal unregelmassig ; Textur grob " it seems more 



FIG. 37. Dijfiugia pyriformis Perty : ? = D. oblonga Ehrenb. After 

 Perty, loc. cit. x about 200. 



probable that it is really a Difflugia, for the tests of 

 the Nebelse can scarcely be said to have a coarse 

 texture. It was considered by Ehrenberg to be the 

 same as his species, for he says : " Si reversa D. 

 oblonga incrustatione detersa ex D. pyriformis oriretur 

 quod Claparede et Lachmann nomen delendum esset." 

 (< Abth. Akad. Wiss. Berlin,' 1871, p. 256.)] 



Ehrenberg's name proteiformis has been adopted 

 by some authors as covering the species now under 

 consideration,* but, we think, without sufficient reason. 



* [The identity of the forms thus named with D. oblonga is so doubtful 

 that the references are omitted in the synonymy.] 



