PLATE 11. 



Structure of Sareotlic Body and Calcareous Disk of OrhltoUtes tenuissima. 



Fig. 1. — Sarcodic body of the central portion of the disk; showing the primordial 

 segment giving off the spiroloculine coil, the sixth turn of which, o, begins to open out 

 into a peneropline form, afterwards becoming divided into rows of orbiculine sub-segments, 

 which are connected together laterally by the continuity of the sarcodic body through the 

 gallery at the outer end of each row, and radially by the stolon-processes that pass through 

 the septal passages, from the gallery of the inner row into the chamberlets of the outer. 

 Nuclear (?) corpuscles are seen irregularly distributed through the sarcodic substance. 

 Masrnified 75 diameters. 



"o 



Fig. 2. — Nuclear (?) bodies, as seen under a power of 450 diameters. 



Fig. 3. — Section of first-formed portion of the disk, laying open the primordial 

 chamber a, and the spiroloculine chambers, partially divided as at h, which coil round it. 

 Magnified 125 diameters. 



Fig. 4. — Portion of the sarcodic body shown in fig. 1, enlarged to 125 diameters, to 

 show the distribution of the nuclear (?) corpuscles: — a, expanded extremity of the last 

 spiroloculine coil ; b, h, h', h\ portions of preceding coils, crowded with nuclear (?) 

 corpuscles ; c, orbiculine sub-segment, with five corpuscles ; (/, d, d, d, orbiculine sul)- 

 segments, each with one or with two corpuscles. 



Fig. 5. — Central portion of the calcareous disk, as seen by transmitted light : — a, ex- 

 panded chamber formed by the termination of the spiroloculine cod, and closed-in by 

 a peneropline septum traversed by four passages ; h, second chamber, divided by radial 

 partition into orbiculine chamberlets ; c, third chaml)er, not here separated from the 

 second by a septum, and having only one radial partition ; d, d, fourth chamber, having 

 at d', d' lateral extensions which begin to enclose the spiroloculine coil ; e, e, fifth 

 chamber, with lateral extensions e', e', proceeding still further backwards ; these chambers, 

 and those that succeed them, divided by radial partitions into orbiculine chamberlets. 

 Magnified 75 diameters. 



