Mr. W. H. Benson on Plectopylis. 243 



Fig. 6. a to d, " Swarmers," swimming in water, assuming various figures 

 of a Eugleniform character. Magn. 390 diams. 



Figs. 7 and 7 sp. A portion of the capillitium of JEthalium septicum. At 

 b is a collection of calcareous matter; sp. spores of the same. 

 Magn. 390 diams. 



Fig. 8. a to e. Spores of JEthalium septicum : a to c, escape of " swarm- 

 ers" from their enclosing integument; c', the swarmer imme- 

 diately after its escape ; d, d', two swarmers furnished with two 

 cilia; <?, a third with one cilium only, as usual. Magn. 390 

 diams. 



Fig. .9. A large Amoeba of jEthalium septicum. 



Figs. 10-13. Amoebae of the same organism, of various sizes, exhibiting 

 their progressive growth. 



Fig. 14. A large Amoeba of ^EtJialium septicum, crawling in the direction 

 of the arrow shown alongside, and showing internally three large 

 vacuoles, but no foreign ingesta. Length T V'"; width J T . 

 Magn. 390 diams. 



Fig. 15. An encysted Amoeba of the same being, having seven spores of 

 jEthalium within it, observed to rotate with the substance around 

 them. Magn. 390 diams. 



Fig. 16. A slightly magnified view of a section of the spore-producing 

 portion of an old ^Ethalium septicum, after being treated with 

 alcohol. The spore-producing sarcode-cords are swollen, and 

 distinguished into a cortical and a medullary portion ; much of 

 the former, however, has been lost in making the section. 



Fig. 17. A small segment of a magnified view of the sarcode-ramifications 

 of jEthalium septicum, showing the secondary pseudopodous 

 processes, a, on the margin. Magn. 90 diams. 



Fig. 18. A portion of the network of sarcode-fibres of^Ethalium septicum, 

 expanded on a glass slide, and viewed by reflected light ; of the 

 natural size. 



Fig. 19. a to n. Spores and their contained or emerged swarmers of 

 Trichia varia. Some seem of a Eugleniform figure, with a fila- 

 ment ; and others Amcebiform, with or without a filament. 



XXVI. Notes on Plectopylis, a group of Helicidse distinguished 

 by several internal plicate Epiphragms ; with the Characters of 

 a new Species. By W. H. BENSON, Esq. 



AN examination of the interior of specimens of Helix Achatina t 

 Gray, received from Moulmein, has revealed a singular and in- 

 teresting internal structure in that shell. This formation occurs 

 also in H. Cydaspis, B. ; the dextrorse variety of H. refuga, 

 Gould, from the Tenasserim Valley ; the species from the banks 

 of the Irawadi (H. Leiophis, B), previously supposed to be a 

 small. variety of refuga; and in a second group from Darjiling 

 and the Khasia Hills, consisting of H. plectostoma and H. 

 Pinacis, B. 



The longest-known shells of the group have been classed with 

 various forms by systematic authors. Helix Achatina and H. 

 refuga were referred by Albers to Atopa, which also includes 

 the Cingalese H. Rivolii, Desh., and H. erronea, Albers, possess- 



