ivith Olservations on their Internal Structure. 173 



Obs. I have already stated that the chambers of tlie central 

 plane (fig. 24) of this genus commence from a central cell. This 

 cell is spheroidal or elliptical, and perhaps a little larger than 

 the generality of those which succeed it ; the next formed is 

 semilunar, and then comes a pear-shaped chamber or two ; after 

 which, the rest, that are in contact with the central cell, are more 

 or less polygonal. From each of these chambers comes off a 

 line of others in a spiral form, which, diminishing abruptly in 

 breadth, terminates upon the back of the preceding one, the first 

 being the shortest ; to this succeeds another series of lines or 

 rows terminating in like manner, but of wider extension ; and so 

 on successively, until the plane, as before stated, appears to be 

 formed of concentric circles. Sowerby's account and figures of 

 the external and internal structure of this fossil (loc. cit.) accord 

 with my own observations ; but Dr. Carpenter (Quart. Journ. Geol. 

 Soc. loc. cit.) I think has been misled in considering the pillars 

 of Sowerby " nothing more than the opake matter filling the 

 perforations ;" since by a proper section, these columns are seen, 

 as before stated, to be the piles of compressed cells (fig. 29), as 

 they ascend from the central plane, surrounded by the " opake 

 matter " to the periphery. It is in this " opake matter " that 

 Dr. Carpenter's " perfox'ations " are situated, that is, in the inter- 

 septal or intercellular spaces, which it partially fills ; his perfo- 

 rations being the orifices of the interseptal vessels described in 

 the structure of the shell of Operculina Arabica [loc. cit.). 



In this species of Orbitoides we have the " stellate lines " uni- 

 ting or as it were supporting the columns of the cells. They 

 consist of bars or vertical septa of opake matter extending from 

 one column to another, in straight lines, but diminishing in 

 thickness towards the central plane, where they become faint 

 and at last disappear altogether. They form the only distin- 

 guishing character between this species and Orbitoides Prattii 

 (see illustrations to Dr. Carpenter's paper, loc. cit.) ; yet I am 

 pretty sure that I have seen them in a section of the latter, near 

 the central plane (where of course they were not present on the 

 surface), just as they are represented in fig. 145 of Dr. Carpen- 

 ter's illustrations, which this author regards as a feature of an 

 undescribed species. Hence I am inclined to the opinion that 

 hycopkris dispansus and Orbitoides Prattii are but varieties of the 

 same fossil. 



I should also here mention, that when the central plane of 

 Lycophris dispansus is ground down to an extreme thinness, an 

 interseptal space appears between the septa and an opake line 

 in the centre of it indicative of the former existence of an inter- 

 septal vessel there, as in Operculina and Nummularia : this is also 

 seen iu Dr. Carpenter's illustrations (fig. 34). 



