FOR AMINIFERA . Ill 



the Eocene Tertiary, but it dates from the Lias, and occurs 

 plentifully in the recent seas. 



The last of the Miliolida which need notice are the aber- 

 rant types, which may be grouped together in a sub-family 

 under the name of Dactyloporidce. 1 The simplest forms of 

 this curious group, such as Dactylopora eruca (fig. 19, a), 

 consist of a series of isolated but coherent chambers, each 

 with a single opening, disposed in a half ring, and either 

 free, or more commonly parasitic on shells, and found in 

 tropical seas at the present day. The fossil forms are similar 

 in structure to the simple type just alluded to, but they form 

 complete rings, and these rings are superimposed upon one 

 another so as to form longer or shorter columns, closed at their 

 lower end but open above (fig. 19, B G). Each ring is 

 quite independent of the others, the orifices of the constituent 

 chambers all opening into the central cavity (fig. 19, c) ; but 

 in some of the fossil forms the place of the chambers is taken 

 by canals, which, like the former, do not communicate with 

 one another (fig. 1 9, F). The various members of the Dactyl- 

 oporidce range from the Trias to the present day, and they 

 have a special interest, from the fact that certain forms of 

 them (Gryroporella, fig. 19, E) constitute vast masses of lime- 

 stone in the Trias of the Bavarian and Tyrolese Alps. 



Coming next to the family of the Lituolida, we have to 

 deal with imperforate Foraminifera, mostly with arenaceous 

 tests, but sometimes sub-arenaceous in texture, and some- 

 times composed of purely calcareous particles embedded in a 

 calcareous cement. In Lituola itself, the type of the group, 

 (fig. 18, d), the test is generally crosier-shaped, sometimes 

 nautiloid, usually with a rough exterior, and composed of 

 sand-grains agglutinated together. The genus ranges from 

 the Carboniferous to the present day. An essentially Car- 

 boniferous type is Endothyra, in which the shell is exactly 

 like that of a Rotalia in shape, and which is found abund- 



1 Of late years high authorities have brought forward strong evidence to 

 prove that most or all of the Dactyloporidce are really calcareous Algce. The 

 question cannot be discussed here in detail ; but until a final decision has 

 been given by specialists in the department of the Foraminifera, it seems 

 safest to retain the group in its present position. 



