Mr. W. H, Benson 07i Plectopylis. 243 



Fif/. 6. fl to d, " Swarmers," swimming in water, assuming various figures 

 of a Eugleniform cliavacf.er. Magn. 390 diams. 



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

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

 Magn. 3.90 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; e, a third with one cilium only, as usual. Magn. 390 

 diams. 



Fig. 9. A large Amoeba of JEthalium septicum. 



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

 their progressive growth. 



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

 of the arrow shown alongside, and showing internally three large 

 vacuoles, but no foreign ingesta. Length iV'"; width 2T • 

 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. ]\Iagn. 390 diams. 



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

 portion of an old ^thulium 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 JEthcdium septicum, showing the secondary pseudopodous 

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



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

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

 natural size. 



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

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

 ment ; and others Amoebiform, 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, 

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

 teresting internal structure in that shell. This formation occurs 

 also in H. Cyclaspis, 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 //. 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 refen-ed by Albers to Atopa, which also includes 

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



