130 



PROTOZOA. 



grouped together under the name of " Perforate Foraminifera," the 

 first family we have to deal with is that of the Textularidce, in which 

 the test may be arenaceous or calcareous, but usually possesses a 

 perforate calcareous basis. The smaller forms of the family have a 



Fig- 35- — A, A specimen of Loftusia persica, from the Eocene of Persia, of the natural size, 

 cut open to show its general plan of structure. (After Brady.) b, Portion of a vertical section ot 

 Loftusia, showing the minute structure of the test, enlarged about ten times. (Original.) 



hyaline calcareous shell, with large pseudopodial foramina. The 

 chambers are usually arranged in two or more alternating series, 

 generally in a straight line, but sometimes in a spiral. In many 

 cases (e.g., in Bigenerina) the test is dimorphous, the first-formed 

 chambers being in a double series, while the later ones are uni- 



serial. In Textularia itself (figs. 29, 

 /, and 36) the test is generally coni- 

 cal or wedge-shaped, and consists of 

 numerous chambers arranged in two 

 alternate parallel series. Bige?zerina 

 is much the same as Textularia, 

 except that the last-formed seg- 

 ments are disposed in a single and 

 not a double series ; and both make 

 their first appearance in the Car- 

 boniferous, the latter being a com- 

 mon type in many formations and being specially abundant in the 

 Chalk. Bulimi7ia (fig. 29, n), dating from the Trias (Rhastic) on- 

 wards, consists of spheroidal segments which progressively increase 

 in size, and form an oblique spiral; while Cassidulina (fig. 29, 111), 

 ranging from the Miocene to the present day, though truly biserial, 

 is more or less completely rolled up, and may thus be regarded as 

 an involute Textularia. Lastly, Chrysidalina, dating from the 

 Chalk, is like Textularia, but is triserial. 



Closely related to the Textularians are the forms included in the 

 small group of the Chilostomellidce, in which the test is many- 

 chambered, calcareous, and finely perforate. The segments follow 



Textularia Meyeriana. 

 D'Orbigny. 



