338 THE MEDALS OF CREATION. Cap. X. 
resemblance between the stipitate Gomphonematz and some 
of the Vorticelle, that I should be still disposed to class 
them as animals, even if Ehrenberg’s observations of the 
retractile threads and snail-like feet of some of the Naviculz 
should not be confirmed.” * 
Thus, whilst referring Closterium, Arthrodesma, Euastrum, 
Xanthidium, Micrasterium, &c. as vegetables, to the Desmi- 
diez, Dr. Bailey places Actinocyclus, Campilodiscus, Coscino- 
discus, Ennotia, Navicula, Gomphonema, Pinnularia, Tri- 
ceratium, &c. among the Diatomacez, as animals. 
Of the animal nature of the microscopic objects which 
now require our attention, there is however no question, 
although the zoological position and affinities of many of — 
the organisms included in this survey are still but imperfectly 
determined. 
The animals designated Foraminifera,t or Rhizopoda,t 
are of a more simple structure than the Polypifera and — 
Echinodermata described in the previous chapters ; yet as 
their relics are for the most part presented to the notice of 
the geologist as aggregations of shells, forming extensive beds 
of limestone, it will be convenient to treat of them in this 
place. 
The fact that the fossil remains of Foraminifera, and 
of Mollusca, alike consist of shells, and constitute strata 
identical in mineral characters, and deposited under like | 
physical conditions, renders the examination of these J/i- 
crozoa § a fit introduction to the study of the durable remains — 
of the higher order—the Mollusca. 
* Smithsonian Contributions, vol. ii. p. 34. 
+ FORAMINIFERA, 7.e. bearing foramina—a name derived from the 
minute openings in the shells and their septa. 
~ Ruizopopa; root-like feet; from the long fibrous processes, or — 
pseudopodia, 
§ Microzoa; from puxpds, mikros, small, and €or, zoon, animal; a — 
= . . . } 
convenient term to denote minute animal organisms whose forms can — 
only be defined by the aid of the microscope. 
Peete Ia 2. 
