Microscopical Society. 2863 



few years ago of a fossil-dealer, in Bristol. The appearance and chemical composi- 

 tion of this specimen, perfectly agreeing with those of the coniferous wood so common 

 in the lias leave no doubt as to this being from that formation. Drawings of its 

 structure were exhibited, leaving no question of this wood being a true non-gymno- 

 spermous exogen ; and its occurrence in the lias was considered by the author as a 

 fact of considerable importance, as proving that trees of that character existed at a 

 much earlier period than has hitherto been generally supposed. 



Mr. Legg read a paper " On the Minute Structure of the Calcareous Shells of 

 some recent Species of Foraminifera," by W. C. Williamson, Esq. In introducing 

 the subject of this paper, the author remarks, that notwithstanding the large amount 

 of attention that has been given to the study of the Foraminifera within the last few 

 years, there is still very much of obscurity resting upon their history ; wide differences 

 of opinion existing as to their true zoological position, and as to the objects compre- 

 hended in the group of animals so designated. After alluding to a former memoir 

 (that on the Polystomella crispa) the author proceeds to describe some peculiar forms, 

 chiefly belonging to the genera Amphistegiua, Orbiculina, and Nonionina, detailing 

 the structure of their calcareous shells, and pointing out the amount of light which 

 they throw upon those of Nummulina and Orbitoides, to which so much attention 

 has recently been paid by Dr. Carpenter and Messrs. Jolie and Leymene. 



On making a horizontal section of the shell of Amphistegina gibbosa, this species 

 exhibits the ordinary contour seen in so many of the Foraminifera; viz., a spiral ar- 

 rangement of cells separated from each other by calcareous septa : a vertical section 

 shows that the object is not only inequilateral ; its inner convolutions especially, being 

 more convex on one surface than on the other, but that the convolutions are not all 

 in one plane; the earliest formed spirals being on a lower level than those of a more 

 recent growth. In the arrangement of the septa, this species differs but little from the 

 ordinary type of the Rotaline forms ; one aperture exists in each septum, communi- 

 cating continuous chambers ; over the inner floor of each cell are numerous calcareous 

 papilla and projecting pillars ; these are considered as secondary growths, deposited 

 after the segment has surrounded itself with a calcareous covering, acting as pillars 

 and buttresses to strengthen the habitation of the creature. In tracing the direction 

 of the spiral outline from the external extremity, the parietes become thickened : the 

 parietes of the shell consist of a great number of parallel laminae, traversed in certain 

 parts by long and well-denned tubes for the transmission of pseudopodia, whilst in 

 other portions (especially the central portion, and the angular external margin of 

 each segment) these tubes are wanting; these lamina are supposed to have been se- 

 creted by the animal exteriorly, and the pseudopodium tubes are continued as each 

 successive layer is deposited ; occasionally, however, the tubes (especially in the 

 umbilical region) have become blocked up by the more recent investments. After 

 thus covering over at least a considerable part of the exterior of the shell with new 

 lamella, the soft animal appears to have retreated to the limited area, which the new 

 segment was ultimately destined to occupy, and here, the new lamella being con- 

 tinuously prolonged, instead of remaining in close contact with the pre-existing shell, 

 have sprung up from its surface in order to form a calcareous investment for the 

 newly formed segment, which would in its turn be invested and rendered dexter by 

 numerous repetitions of the same process. 



A portion of the horizontal section of Amphistegina Antillarum was described as 

 having an addition to the ordinary arrangement of the septa common to the genus, 



