290 On a new Type of Carboniferous Foraminifera. 



died out has long been known to be untenable. It has been 

 shown that there is no material distinction, except in size, 

 between the Nummulite of the Eocene period and that now 

 living in southern and tropical seas. On the other hand, Dr. 

 Giimbelof Munich has described a Nummulite (N. jurassica*) 

 from a Jurassic limestone of the zone of Ammonites tenuilobatus. 

 And, referring to a much earlier paper, we find that Rouillier 

 and Vosinsky in 1849 f figured, under the name of Nummidina 

 antiquior, an unsymmetrical Foraminifer, one fifth of an inch 

 or more in diameter, from the Carboniferous Limestone of 

 Miatchkovo in Russia. Though not altogether overlooked, 

 this paper seems to have attracted but little attention until very 

 lately ; but the figures accompanying it, although deficient in 

 the structural details which we should expect from more modern 

 drawings, leave little doubt that they represent a true Nummu- 

 lite. Since then Eichwald J has described, under the name of 

 Orolrias cequalis, what is apparently only a more symmetrical 

 lenticular variety of the same organism, obtained from the 

 same Carboniferous Limestone. It is not without interest, in 

 connexion with the geological distribution of the Nummulinida, 

 that some Carboniferous material collected for me by my friend 

 W. W. Stoddart, F.G.S., of Bristol, from the Clifton rocks, 

 contains an Ampliistegina, undistinguishable from the A. 

 vulgaris of D'Orbigny, though of very small size. I am not 

 aware that any specimen of this genus has hitherto been found 

 earlier than the beginning of the Tertiary epoch. 



EXPLANATION OF PLATE XL 



Figs. 1 a & 2. Archcedisciis Karreri, side views. Magnified 38 diameters. 



Fie/. 1 b. Periphevo-lateral aspect of 1 a, showing the open end of the 

 tube, forming the general orifice. Magnified 38 diameters. 



Fig. 3. Longitudinal section. The shell-wall has scarcely any thickening 

 on the median plane, as shown in the outer circlets of this section. 

 Magnified 38 diameters. 



Fig. 4. Transverse section, showing the thickening of the walls on the 

 lateral surfaces, especially near the centre, and the extensive 

 tubulation. Magnified 38 diameters. 



Fig. 5. Lower portion of the same section, magnified 230 diameters, 

 showing the two distinct sorts of tubuli, and the indications of a 

 primary shell-wall as distinct from the thickening matter. 



Fig. 6. Part of the transverse section of another specimen, magnified 230 

 diameters, showing successive layers of shell-deposit due to the 

 prolongation of the crescentiform edges of the tubular shelly in- 

 vestment over the lateral surfaces of the test. 



* Neues Jahrbuch fur Min. &c, Jahrg. 1872, pp. 241-260. 

 t Bulletin de la Societe Imperiale des Naturalistes de Moscou (1849), 

 vol. xxii. p. 337, pi. K. figs. 60-78. 



X Letliflea Rossica (I860), vol. i. p. 353, pi. 22. fig. 16. 



