. The microscope and its revelations. seen at f>. h. fig. 634. At of horizontal section ofNummulites showing the structure of thewalls and of the septa of the chambers :«, a, a, portion of the wall covering threechambers, the punctations of which are theorifices of tubuli; b, b septa between thesechambers containing canals which send outlateral branches, c, c, entering the chambersby larger orifices, one of which is seen at (1. IS certain other points, d. d, d,fig. 632, the shell-substanceis not perforated by tubes, butis peculiarly dense in its texture, forming solid pillars which seemto s
. The microscope and its revelations. seen at f>. h. fig. 634. At of horizontal section ofNummulites showing the structure of thewalls and of the septa of the chambers :«, a, a, portion of the wall covering threechambers, the punctations of which are theorifices of tubuli; b, b septa between thesechambers containing canals which send outlateral branches, c, c, entering the chambersby larger orifices, one of which is seen at (1. IS certain other points, d. d, d,fig. 632, the shell-substanceis not perforated by tubes, butis peculiarly dense in its texture, forming solid pillars which seemto strengthen the other parts; and in Nummulites whose ,have been much e.\|>>,•<! to attrition, it commonly happens that thepillars of the superficial layer, being harder than the ordinary shell-substance, and bein»- consequently less worn down, are left as 3 H §34 MICROSCOPIC FORMS OF ANIMAL LIFE. PIG. 634,—Internal cast of two of the cham-bers of atrintti, with thenetwork of canals, It, in the marginalcord communicating with canals passingbetween the chambers. prominences, the presence of which has often been accounted (buterroneously) as a specific character. The successive chambers of thesame whorl communicate with each other by a passage left between the inner edge of the partitionthat separates them and the marginal cord of the pre-ceding whorl ; this passage issometimes a single large broadaperture, but is more com-monly formed by the more orless complete coalescence ofseveral separate perforations,as is seen in fig. 631, b. Thereis also, as in Operculina, avariable number of isolatedpores in most of the a secondary means ofcommunication between thechambers. The canal systemo£Nummulites seems to bear-ranged upon essentially thesame plan as that of Oper-culina ; its passages, however, are usually more or less obscured by fossilising materia
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectmicrosc, bookyear1901
