210 PHOF. W. J. SOLLA.S OX SACCA:MMI^A CAETEET, [vol. Ixxvii, 



presents the same minute structure as is met with in fossil Imper- 

 forata. such as Jlilioln and Alreolites : that is, it is minutely 

 granular, and so imperfectly transparent that extremely thin slices 

 m.ust be prepared for its examination under the microscope. In 

 this particular it presents a striking contrast to associated vitreous 

 forms such as Arclicediscv.s ; and I am inclined to think that it was 

 the minute structure of the shell rather than the thickness of his 

 slices which led Carj)enter to doubt whether it was perforate or 

 not. That it is as completely perforate as any vitreous foraminifer 

 was first shown by Baron Miiller, and with sufficiently thin slices 

 anyone may convince himself on this point, the canals being 

 perfectly obvious (whether seen in longitudinal or in transverse 

 section). 



Apparently then, Fusidina is as typical a porcellanous form as 

 Alveolites and as typical a Perforate as yumnudites. If so, the 

 distinction between Perforata and Imperforata is deprived of one 

 of the most important arguments in its support. 



But, since this was written, my attention has been called to some 

 observations by Prof. Henri Douville,i who, fi'om a study of un- 

 usually well-preserved examples of Fu.sulina from Laos, is led to 

 assert that the supposed pore-canals can be seen to terminate 

 blindly and even in pouches. Thus the perfoj'ations of Fusulina 

 would seem to have no more significance than the blind canals of 

 JPenerojdis. 



A possible objection however may be raised here ; it has repeated!}' 

 obtruded itself on my mind when reflecting on the supposed pores 

 of SpiriUina. Is it certain that all the perforations of Fasv.Una 

 are of the same nature r If they are. then it becomes impossible to 

 suppose that they are produced by external parasites, and interesting 

 questions suggest themselves as to the relation of the tubulations 

 to the animal, — how they arise and are maintained, what is their 

 function, and so forth. 



Peturning now to the problem with which Ave set out — the 

 taxonomic position of Saccammina carter i — we may first enquire 

 how far the structure of various foraminifera is ^^reserved in the 

 fossi] state. 



The Perforata g-enerallv retain their structure, even when traced 

 far back into the remote past and under very various conditions of 

 environment. Occasionally, however, examples may be met with 

 in which the perforations have disappeared and the wall has been 

 converted into a mosaic, one crystal thick, with no remaining traces 

 of the original structure, ^odosaria from some localities in the 

 Upper Lias affords an example, but the same genus from other 

 localities of the same age preserves to a considerable degree its 

 original characters. In the Cambrian System the Xodosaridre can 

 only be determined by their form. 



^ • Les Calcaires a Fiisiilines cle rindc-Chiiie " Bull. Soc. Gtol. France, ser. 4, 

 vol. vi (1907) pp. 576-87. 



