PYXIDICULA OPERCULATA. 21 



mistakes of others, nor his own, should now form 

 the type of the preceding genus [Cyclotella] from this 

 same species, prescribing the name at first proposed 

 but altering the sense ; and at the same time should 

 describe, as a new species of Pyxidicula, the P. oper- 

 culata of Bailey, which seems either identical with 

 that of Ehrenberg or very similar to it and to that 

 so described and figured by the authors named above." 

 He adds his opinion that the specimens of Brebisson 

 and Leonardi in his possession belong to Gydotella 

 and not to Pyxidicula. It is evident that he believed 

 Pyxidicula operculata to be the correct name for this 

 species, and, had he not been merely annotating 



d 



FIG. 166. Pyxidicula operculata : a, vertical view ; b, side view, show- 

 ing furrow by which the test separates, c, showing a transparent 

 globular body ; d, a detached half, x 550. (After Pritchard.) 



Kuetzing's memoir, ' Die kieselschaligen Bacillarien 

 oder Diatomeen,' he would have adopted that name. 



By all the above-named and some other writers 

 Pritchard, Brightwell, and Perty this creature was 

 considered to be a diatom. It was first determined 

 to be a rhizopod by Carter, who found it in the island 

 of Bombay, but he wrongly referred his specimens 

 to the Arcella patens of Claparede and Lachmamu 

 He says that it is very like Ehrenberg's Pyxidicula 

 opercidata, placed by him amongst the Diatomese. 

 This appears to be his reason for rejecting it as a 

 Pyxidicula, and he adds that he thinks " much alliance 

 will be found to exist between the Rhizopoda and the 

 Diatomaceae." It was the opinion of Meneghini and 

 some other naturalists that the diatoms were animals^ 

 and by Ehrenberg not only the diatoms but also the 



