124 On the Microscopical Siliceous Polycystina of Barbados, 



The following tabular survey of Ehrenberg's description of the 

 Barbados animalcules exhibits the large new group of Polycys- 

 tina, which, as will be observed, now consists of 282 species, sub- 

 divided into seven families and forty-four genera. The nature of 

 the limitation of the individual animals, and in the individuals, 

 the apertures in the shield, of which the anterior aperture is ge- 

 nerally lattice-like or fenestrate, and the posterior one open, have 

 been used in a physiological point of view to furnish the import- 

 ant and necessary characters for the greater divisions, subdivi- 

 sions, and generic differences of the group. 



Testae apertura 

 unica (simplex' 

 aut cancellata) 



A short Systematic Arrangement of the Families of Cellular 

 Animals. 



Polycystinorum Familia. 



I. — Polycystina solitaria. 

 Testae siliceae spatio interno ample pervio aut passim levius transverse 



constricto. 

 Spatium internum liberum 



(articuli, dissepimenta, Gen. Sp. 



stricture nulla) I. HaMcalyptrina. III. 13 



n Spatium internum strictu- 

 ' J ris articulatim contrac- 

 ts turn II. Lithochytrina. YII. 31 



Testae apertura duplex, anterior saepius can- 

 cellata, posterior tota aperta III. Eucyrtidina. XV. 149 



II. — Polycystina composita. 



Testae siliceae spatio interno celluloso aut strictura longitudinali constricto. 

 'Cellulae binae clathratae nu- 



cis forma amplae, stric- 

 tura longitudinali levius 



discretae IV. Spyridina. V. 36 



Cellulae numerosae parvae, 



ordine concentrico, spi- 



rali aut nullo (spongiose) 



in orbes consociatae, in- 



terdum radiatae 



Simplices, subglobosae aut 



lenticulares, interdum 



margine simpliciter ele- 



gantissime radiatae .... 

 Parte media nucleata (ocel- 



lata) margine subconcen- 



trice, celluloso aut spon- 



gioso (forma complanata 



orbiculari interdum ele- 



ganter lobata et stellata 



aut margine radiata) . . VII. Lithocyclidina. IV. 8 



XLIV. 282 



Testae nucleo 

 destitutae (as- . 

 sociatae et coa- 

 litae) 



Testae nuclea- 

 tae (involutae) «^ 



V. Calodictya. VI. 15 



VI. Haliommatina. IV. 30 



