148 THE MICROSCOPIST. 



forming a zigzag chain ; vittse two, longitudinal, inter- 

 rupted, and more or less figured ; marine. 



TRIBE III. AREOLAM. Valves circular, with cell-like 

 (areolar) markings, visible by ordinary illumination. 



SUB-TRIBE 1. DISCIFORMES. Valves alike, without ap- 

 pendages or processes. 



COHORT 14. COSCINODISCE.E. Valves circular. 



64. Actinocydus. Fr. solitary; v. circular, undulate, 

 the raised portions like rays or bands radiating from the 

 centre, which is free from markings ; marine and fossil. 



65. Actinoptychm. Fr. as Actinocydus, but radiating 

 internal septae, as well as rays. 



66. Coscinodiscus . Fr. single ; v. circular, areolar all 

 over ; marine and fossil. 



67. Aracknoidiscus. Fr. single ; v. circular, not undu- 

 late, with concentric and radiating lines, and intermediate 

 areola absent from the centre (pseudo-nodule); marine 

 and fossil. 



68. Asterolampra. Fr. single ; v. circular, finely areolar, 

 except in the centre and at equidistant clear marginal rays 

 radiating from the centre, which is traversed by radiating 

 dark lines (septa), alternating with the marginal rays ; 

 fossil. 



69. Aster omphalos. As Asterolampra, but two of the 

 central dark lines parallel, and the corresponding mar- 

 ginal ray obliterated ; fossil. 



70. Halionyx. Fr. single ; v. circular, without septa, 

 with rays not reaching the centre, and with intermediate 

 shorter rays ; between the rays transverse areolar lines ; 

 fossil. 



71. Odontodiscus. Fr. single, lenticular ; v. covered 

 with puncta (areolee), arranged in radiating rows on ex- 

 centrically curved lines, and with erect marginal teeth ; 

 fossil. 



72. Omphalopelta. As Actinoptychus, but upper part of 

 margin of valves with a few erect spines ; fossil. 



