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CARBONIFEROUS AND PERMIAN FORAMINIFERA. 



surface. Precisely the same effect, arising from the same cause, is to be observed in some 

 Jurassic Trochamminm. 



Moreover, in Endothyra the septation is never double as in the higher Rotalines ; that 

 is to say, each succeeding chamber is a mere tent-like covering of a lobe of sarcode lying 

 directly upon the preceding segment, and not a complete investment of the lobe by a 

 shell-wall proper to itself, as in Rotalia (Carpenter's ' Introd. Foram.,' p. 212). 



Whilst these characters are sufficient to separate Endothyra from the Rotaline types, 

 and also from the genus Nonionina, with which the isomorphism is less constant, the close 

 resemblance in form, and analogy in range of morphological variation, indicate a similarity 

 in laws of growth and in conditions of existence that demand recognition in any natural 

 system of classification. There can be little doubt, notwithstanding the imperforate and, 

 to some extent, cemented or composite structure of the test in Endothyra, that the type 

 has a much closer relationship with the Rotaline series than with rough arenaceous genera, 

 such as Lituola and its near allies. As has been already stated, the systems of classifica- 

 tion of the Foraminifera at present in use whether in this country or in Germany, however 

 otherwise differing, agree in the adoption of " shell-texture " as the basis of the primary 

 divisions, and groups like the one under discussion, which seem to be somewhat out of 

 place whatever position may be assigned to them, serve to remind us how rarely any 

 classification having a claim to be considered natural can be arranged in a single linear 

 series, with its constituent groups separated by definable lines. 



With this explanation a place may for the present be assigned to Endothyra amongst 

 the arenaceous Imperforata of which it may be regarded as the highest of the minute 

 and simple forms, its nearest allies therein being the rotaliform Valvulinee and the genus 

 Involutina. Apart from schemes of classification, Endothyra may either be taken to 

 represent a transition group intermediate to the spiral Lituolida and the true Rotalines, 

 or, as there is much reason to think, it may represent a primitive type from which or 

 through which, more than one series of Foraminifera, widely differentiated in their later 

 developments, have had their origin. 



So far as is known the genus Endothyra is confined to the Carboniferous Epoch, its 

 nearest allies in rocks of later age being amongst the Rotaline genera. 



Endothyra Bowmani, Phillijjs, PI. V. figs. 1 — 4. 



Endothyra Bowmanni, 1 Phillips, 1845. Proc. Geol. and Polytech. Soc. "W. Riding 



Yorks.,vol. ii, p. 279, pi. vii, fig. 1. 

 Rotalia Baileyi, Hall, 1856. Trans. Albany Inst., vol. iv (p. 24 of the Memoir). 



1 By an oversight, of a sort unusual with the late Professor Phillips, this species, named after 

 Mr. J. 0. Bowman, appears as "Bowmanwi." The slight correction made is, I believe, consistent with 

 usage. 



