THE MICROSCOPE IN HISTOLOGY AND BOTANY. 149 



73. Symbdoph&ra. Fr. single, disk-shaped ; v. with in- 

 complete septa radiating from the solid angular umbili- 

 cus, and intermediate bundles of radiating lines ; marine 

 and fossil. 



74. Systephania. Fr. single ; v. circular, areolar, with- 

 out rays or septa, with a crown of 'spines or an erect 

 membrane on the outer surface of each valve ; fossil. 



COHORT 15. ANGULIFERA. Valves angular. 



75. Amphitetras. Fr. at first united, afterwards sepa- 

 rating into a zigzag chain, rectangular; v. rectangular, 

 the angles often produced ; marine. 



76. Amphipentms. Fr. solitary ; v. pentangular ; fossil. 



77. Lithodesmium. Fr. united into a straight filament ; 

 v. triangular, one side plane, the others undulate ; marine. 



TRIBE IY. APPENDICULAT^E. Valves with processes or 

 appendages, or with the angles produced or inflated. 

 COHORT 16. EUPODISCE^E. Fr. disk-shaped; v. circular. 



78. Eupodiscus. Fr. single, disk-shaped ; v. circular, 

 with tubular or horn-like processes on the surface ; aquatic 

 and marine. 



79. Auliscus. As Eupodiscus, but processes obtuse and 

 more solid ; fossil. 



80. Insilella. Fr. single, fusiform ; v. equal, with a 

 median turgid ring between them ; marine. 



COHORT 17. BIDDULPHIE.E. Fr. flattened; v. elliptical 

 or suborbicular. 



81. Biddulphia. Fr. rectangular, more or less united 

 into a continuous or zigzag filament; the angles inflated 

 or produced into horns ; v. convex, centre usually spinous ; 

 marine. 



82. Isthmia. Fr. rhomboidal or trapezoidal, cohering 

 by one angle ; angles produced ; marine. 



83. Chcetoceros. Fr. compressed ; v. equal, with a long 

 spine or filament on each side ; marine. 



