Stride of Foraminiferous Tests. 139 



of cleavage. In some instances the fossilized Nummulite 

 breaks out in rhombs like the fossilized test of an Echinoderm ; 

 this also may be worth remembering. 



The organic structure, on the other hand, consists of 

 cavities called " chambers " superposed upon each other with 

 straight tubes running between them, and a dendriform 

 branched canal-system, which pervades the whole Nummu- 

 lite, both opening on the surface — the former through the 

 intervention of the chambers, and the latter by themselves. 



Such is the general structure of the Nummulite, which, so 

 far as the "organic " part goes, it is as well to premise can in 

 its totality or " system " be seen only in an infiltrated fossilized 

 specimen, or in a recent one (ex. gr. Operculina arabica) whose 

 canal-system has been filled with carmine. 



Now, taking the chambers and their connecting tubuli first, ' 

 we may easily arrive at the principle upon which this structure 

 has been elementarily built by figuring to ourselves a narrow 

 cone with its pointed end downwards, and this cone composed' 

 of half a dozen or more lenticular chambers, and as many 

 short cylinders with concave ends, respectively piled upon 

 each other, beginning with a cell or chamber at the bottom 

 and ending with a cylinder at the top,' whose end in the un- 

 worn state is more or less convex, to correspond with the 

 surface of the test. Further, conceive that each of the cylin- 

 drical portions consists of a mass of parallel tubuli running 

 perpendicularly between each pair of chambers ; and, lastly, 

 place a sufficient number of such cones together, with conical 

 portions, composed of shell-substance only, here and there 

 between them, having all their sides respectively in contact 

 throughout, and you will have a prismatic or columnar struc- 

 ture which in the aggregate must form a globular or doubly 

 convex test, as the case may be. On account of the difference 

 in the form of the chambers, this will be more like an Orbitoides 

 than a Nummulite ; but the principle of structure is the same 

 in all. Of the " dendriform branched canal-system," which 

 pervades the whole Nummulite outside the chambers, suffice 

 it to say that siliceous casts of this present a smooth surface ; 

 while those of the chambers, towards the tubuli, present a 

 granulated surface corresponding to the ends of the tubuli, 

 which are conical. 



Still, as the " stria? " and the " tubuli " all radiate from the 

 centre, the former are very likely to be confounded with the 

 latter in the wmnfiltrated specimen. This is well proved by 

 the woodcut which Dr. Carpenter has introduced from one of 

 D'Archiac and Haime's illustrations ('Annals,' vol. xiii. p. 457, 

 June 1874) to " dispose of the objection " which I have urged 



