162 



as many visible simple apertures. On the other hand, the number of 

 minute very extensile tentacula which at the same time effect the lo- 

 comotion, and which project as it were from all parts of the sieve-like 

 shell, evidently resemble the contractile fringes of the Flustrat, and of 

 the marine Gasteropods. 1 ' (Taylor's * Scientific Memoirs,' vol. iii. 

 p. 342, 1842). And again, "I never observed siliceous Infusoria in 

 the intestines of Geoponus, but in these associated animals, the space 

 is certainly closed for each individual, and consequently much more 

 confined than in the single animals of Nonionina. After dissolving 

 the shell with acid, where Dujardin found only a body remaining be- 

 hind in the Rotalia, I was enabled, by a very slow process, to discover 

 in both, also, a completely spiral, articulated, inner body, the single 

 articulations of which were connected in Nonionina by one, in Geopo- 

 nus by eighteen to twenty tubes (siphones) as connecting parts of as 

 many individual animals, lying close to one another in each articula- 

 tion." (Idem. p. 348). 



M. D'Orbigny, speaking of the Polystomella, says, " Les Polysto- 

 melles se distinguent des tous les genres de Nautiloidees par ce ca- 

 ractere singulier, que les ouvertures du bord de la derniere loge, 

 reparaissent en fossettes, plus ou moins allongees sur toutes les autres : 

 les dernieres seulement ouvertes, les autres toutes fermees. II en re- 

 sulte qu' exterieurement ce genre se distingue de suite par ce grand 

 nombre de petits excavations transversales, qu' on remarque sur 

 toutes les especes; ('Voyage dans l'Amerique Meridionale,' tome 5me. 

 p. 29) ; and in his description of the genus, he also adds, " Ouvertures 

 nombreuses, eparses en bordure, ou formant un triangle a la partie 

 superieure de la derniere loge, et se montrant encore ouvertes 

 dans les fossettes suturales des dernieres loges." (Idem.) 



None of these descriptions apply either to the shell or to the 

 soft animal of the British Polystomella ; but before making any fur- 

 ther general observations on this topic, I will state the results of my 

 examination of our species. 



This exquisite microscopic object has long been well known as a 

 common organism amongst the sands of our shores, especially on the 

 south and west coasts of the British islands. It is variable in 

 its form, being sometimes broad and depressed, with the margin so 

 thin as to be almost carinated ; whilst in others it approaches to 

 a more spherical form, the keel being thick and rounded. The peri- 

 phery is sometimes entire ; at others each of the smaller chambers, 

 especially, has projecting from its anterior angle a small tubercular 



