172 FAMILY GLOBIGERINIDA. 



A nearer approximation to what we consider the true view of their affinities is presented 

 by the system of Prof. Schultze (xcvii) ; who separates Orbulina and Spirillina {Cormispira, 

 Sch.) from his other Monothalamia, and brings together Rolalida, Teaiilarida, and Cassi- 

 (Miirida, with Vvcllida, as sub-families of his family Turbinoida, which holds very much 

 the same relation to his family Nautiloida, that our family Globigerinida holds to our 

 NuMMULiNiDA. If Prof. Schultzc had expunged his UveJIida from the former, and his 

 CristeUarida from the latter, and had united these with his family Nodosarida, his general 

 arrangement would have differed in this part but little from ours, except in the complete 

 line of demarcation which he draws between the monothalamous and the polythalamous 

 forms characterised by essentially' the same type of structure. On one point, however, 

 we are altogether at variance with him ; namely, the value he assigns to his Family Acer- 

 VULINIDA, which consists of what is in our view but an aberrant form of the Rotaline type, 

 that is distinguished by its "wild" or acervuline growth, the segments being piled one upon 

 another without any definite plan. 



272. Taken as a whole, our family Globigerinida may be considered as holding an 

 intermediate rank between our Lagenida and our Nummulinida. In common with the 

 former, it has its root (so to speak) among the Monothalamia, from which it extends itself 

 upwards in various directions, like a tree whose trunk early subdivides into branches. But 

 whilst the development of the Lagenida is checked at a low grade, so that even their most 

 elevated forms present very little real advance upon the most simple, that of the Globige- 

 RiNiD.i goes on so much further, that we find in the highest types of this family a com- 

 plication of structure scarcely inferior to that which characterises the highest Nummulinida. 

 When we come, however, to consider the relations of the principal generic types of this 

 family, both among themselves and to other groups, we find that they cannot be 

 expressed by any linear arrangement ; and the only practicable method, therefore, is to 

 follow that which seems to be the line of most intimate relationship so far as it may lead, 

 and then, returning to the original starting-point, to take a fresh departure in some other 

 direction. 



273. There can be no hesitation in regarding the monothalamous forms as being those 

 which present the fundamental or essential " idea" of this group under its simplest aspect : 

 and yet these are differentiated from each other by very marked characters ; — Orbulina being 

 often destitute of any pi-incipal aperture, but having numerous secondary apertures of larger 

 size than the ordinary pores ; Oviditcs, on the contrary, presenting an aperture at each end 

 of its egg-shaped chamber ; whilst in Spirillina the single chamber is elongated into a nearly 

 cylindrical tube, coiled upon itself into a spire, which, closed at its central extremity, is freely 

 open at its peripheral. In the two former, as in the Gromida and in Layena, the act of 

 gemmation consists in the production of a segment, which (except in certain cases of mon- 

 strosity) detaches itself from the original body and forms its own separate investment ; but 

 in the latter it consists in a simple elongation of the sarcode-body and continuous extension 

 of the sliell, without any appearance of segmentation. It is obvious that from either of these 

 monothalamous types an ordinary polythalam may be derived ; for, on the one hand, the 

 segments successively budded off from a globular Orbulina may remain in continuity with 



