GENUS ORBITOLITES: HISTORY. 187 



discovery of this remarkable point of structure, have been specially directed to the 

 determination of the extent to which it presents itself in the different sections of the 

 group, and of its value as a distinctive character; and I think that I shall be able to 

 show that it is a feature of the utmost importance, the presence of which marks an 

 elevation of type, and its absence a corresponding degradation. 



It is much to be regretted, that the recent investigations of Professor SCHULTZE 

 should have been so entirely restricted to the structure of the animal, which can 

 only be ascertained in a comparatively small number of cases ; and that he should 

 have failed so completely in the determination of the internal organization of the 

 shell*, which in a large proportion of instances is the only guide we possess to the 

 nature of the being which formed it. The new classification which he proposes, 

 whilst in many respects an improvement upon that of M. D'ORBIGNY, is essentially 

 vitiated by this defect; and being in itself, therefore, just as provisional as that for 

 which it is proposed as a substitute, can scarcely be expected to supersede it. My 

 own researches I offer simply as materials to serve as a basis for classification ; feeling 

 assured that the time is not yet come, in which the superstructure can be erected with 

 any prospect of permanent stability. 



I shall commence with a minute analysis of one of the lowest types, Orbitolites ; 

 and propose to show hereafter, that Orbiculina and Alveolina, though ranked in a 

 different order by M. D'ORBIGNY, are in reality closely allied to it ; whilst a new genus 

 (Cycloclypeus), which, in M. D'ORBIGNY'S arrangement, would rank close to Orbitolites, 

 is physiologically separated from it by the widest possible interval. 



Genus ORBITOLITES. 

 I. History, 



1. The Orbitolite has been chiefly known, until very recently, rather by its fossil, 

 than by its existing forms. The abundant occurrence of its disks in the Calcaire 

 grassier of the Paris basin, early attracted attention ; but Orbitolites were not clearly 

 distinguished by the older observers from Nurnmulites, and their true nature was 

 entirely misunderstood. Thus we find them designated, often in association with 

 Nummulites, under the title of Umbilicus marinus by PLANCUS (BIANCHI), who 



* Professor SCHTJLTZK states (op. cit. p. 15) his inability to discover the canal-system above described ; and 

 as there is no question of his competency and accuracy as an observer, I can only impute his failure to his 

 ignorance of the proper mode of preparing thin sections of these minute shells ; which consists in cementing 

 them to a slip of glass by hardened Canada-balsam ; grinding them down as far as may be desirable on one 

 side ; then loosening them by heat and turning them over, so that the flattened surface shall now be attached ; 

 and finally grinding down the other side, until the requisite degree of thinness shall have been attained; after 

 which a drop of liquid Canada-balsam is laid upon the specimen, gentle warmth applied, and a cover of thin 

 glass put on. Having myself thus prepared sections of Faujasina, which answer in every respect to the figures 

 accompanying Professor WILLIAMSON'S memoir above cited, I can bear the most explicit testimony to their 

 exactness. 



