536 
DE. CAEPENTEE’S EESEAECHES OX THE rOEA3imFEEA. 
contigus, non apparens au-dehors, et rayonnee a rexterieur par des sillons on des cotes 
qui traversent la direction des tours. Ouverture composee de plusieurs trous diverse- 
ment disposes.” The genus was 'soon afterwards adopted by M. d’Oebigxt in his first 
systematic classification of Foraminifera* ; and he seems also to have adopted La^ueck's 
idea of the structure of this type, which he defines as follows f : — “ Les Polystomelles se 
distinguent de tons les genres de Nautiloidees par ce caractere singulier, que les ouver- 
tures du bord de la derniere loge reparaissent en fossettes, plus ou moins allongees. sur 
toutes les autres ; les dernieres seulement ouvertes, les autres fennees. II en resulte 
qu’exterieurement ce genre se distingue de suite par ce grand nombre de petits exca- 
vations transversales, qu’on remarque sur toutes les especes.” He elsewhere adds to 
this description : “ L’animal fait sortir des filamens non seulement par des ouvertui'es du 
dessus de la derniere loge, mais encore par des pores des cotes des dernieres ” ij;. The 
same definition is more concisely repeated by M. d’Oebigxt in his latest publication on 
the subject, notwithstanding that the true structure of Polystomella crista had in the 
mean time been elucidated by Professor Williamson in his admirable memoir on that 
species ; the genus Polystomella being still defined (in the ‘ Corn's Elemcntaire de Pale- 
ontologie et de Geologie Stratigraphiques,’ tom. ii. p. 197) “ Coquille nautiloide, poiu'vue 
de nombreuses ouvertures sur la derniere loge et sur les cotes de la coquille ; une cante 
simple au loges.” 
174. I have already referred, in my General Introduction, to the elaborate inquiiy of 
Professor Williamson into the organization of Polysfomella crisjja^, as ha^ing not only 
established several important facts in regard to its minute structure, but as ha'sing fm- 
nished the starting-point for all future investigations of the same kind : it now becomes 
necessary that I should somewhat fully recapitulate the most important features of his 
description, in order that it may be seen in what points my omi iuquii'ies upon a more 
developed form of the same group have evolved results supplementary to his. To the 
accuracy of his descriptions I can bear the fullest testimony; having not only had the 
opportunity, through the kindness of Professor Willi aaison, of examming the prepara- 
tions still in his possession both of the shell and of the animal of Polystomella O'isjpa, 
but having carried out an independent investigation upon specimens collected by 
myself. 
175. On the exterior of each of the segmental dhisions of the shell of P. cn'spa, strong 
transverse crenulations present themselves, which are deepest near the convex margin of 
the preceding septal band, where they terminate somewhat abruptly, and usually dis- 
appear before reaching the concave margin of the subsequently-formed chamber. The 
depressions between the elevated ridges, which are the “ fossettes ” of M. d’Oebignt, 
often present the appearance of orifices ; but this appearance is fallacious, smee at no 
* “ Tableau Methodique dc la Classe des Cephalopodes,” in Auuales des Sciences Xaturelles, 1S26. 
t Voyage dans I’Amerique Meridionale, tom. v. p. 29. 
t Eoraminiferes Eossiles de Vienna, p. 121. 
§ Transactions of the Microscopical Society, Eirst Series, vol. ii. p. 159. 
