Tijpc of Cuihumferuus Forruainifera. 287 



terous Limestone my attcutlon has been occupied by certain 

 minute discoidal bodies sing-ularly devoid of the sort of external 

 characters which give promise of interest in investigation. 

 The organisms alluded to do not occur in any great numbers ; 

 but a few specimens may generally be found amongst other 

 Ehizopoda in the debris of tbssiliferous limestone beds. 



The bodies in question are lenticular disks, seldom more 

 than a twenty-fifth of an inch in diameter, and a fiftieth of an 

 inch in thickness, and never quite symmetrical. They often 

 present an appearance as though of laminated sti-ucture, and 

 in this, as in some other features, present a superficial re- 

 semblance to very small Nummulites. In the absence of 

 marked external characters the only method of learning their 

 true nature was by means of microscopical sections, which, in 

 bodies so small, were not made witliout difficulty. The trouble 

 involved, however, was amply repaid ; for it unfolded a structure 

 of great interest, especially in its relation to some already well- 

 known types of Foraminifera. I will endeavour, with the help 

 of drawings, to describe this, and to state what I believe to be 

 its significance. 



The interior will be best understood by comparing it to a 

 tube coiled upon itself in constantly varying directions, the 

 periphery being determined by the last circlet of the coil. The 

 tube, wliich represents the cavity occupied during life by the 

 main body of the animal, is never, so far as I have been able 

 to discover, subdivided into chambers. It gradually increases 

 in size with each successive turn — its earlier portion, in one 

 specimen which I have measured, having a transverse diameter 

 of about y— of an inch, the later portion -—-o of an inch ; 

 but in most cases the disproportion is scarcely so great as these 

 figures imply. 



Its shape also varies considerably: — the transverse section at 

 times representing about three quarters of a circle, the truncate 

 or flattened side facing inwards ; at others showing an irregu- 

 larly crescentic or saddle-shaped contour, the concave surface 

 of which embraces more or less portions of the preceding turn 

 of the coil. The coil terminates externally in the periphery 

 of the disk 5 and most of the specimens I have examined liave 

 an appearance as if a portion of the end of the tube had been 

 broken away (as sometimes observable in Nummuh'na) , owing 

 probably to tlie greater delicacy and tenuity of the newly 

 deposited shell-substance. The mouth of tlie tube, representing 

 the general aperture of the shell, appears to have been not con- 

 stricted or otherwise closed in. 



A coil, formed as I have endeavoured to describe, Avould 

 naturally present an irregular surface, were the walls of the 



20* 



