515 



but feel surprised at the tenacity with which the more restricted view 

 is held. But to show whether it is our opponents, or ourselves, who 

 labour under " defective observation," we have given a representation 

 of a portion of the " nummuline layer" in Plate XLL, Fig. 1, taken 

 from one of Dr. Carpenter's sections, magnified 120 diameters, which 

 we have decalcified.* 



At d is represented a portion of the "nummuline layer," in this 

 instance, consisting of distinctly separated aciculi. The separations 

 were filled up with carbonate of lime or calcite, now dissolved out. 

 At a, is another portion with the aciculi in perfect contact. At b, the 

 aciculi or fibres, as they must now be called, present a somewhat modi- 

 fied aspect, being neither "glistening white," nor "cylindrical," as in 

 the previous places; but having the usual colour of serpentine, and the 

 structure of chrysotile or asbestos. At a, the last modification is in 

 an incipient state ; the fibres, in this case in the serpentine, being re- 

 presented by mere incised lines, individually more or less interrupted 

 in their continuity, and varying in their distance from one another. 



We have next to draw attention to anothtr example in the same 

 section (more or less paralleled by many others in it), which equally 

 proves that the above four varieties of the " nummuline layer" are no 

 more than modifications of one type. 



In Figure 2, the letter A denotes a wide opening, formerly filled with 

 calcite or the " intermediate skeleton," lying between two portions of 

 serpentine constituting "chamber casts." The low side, at d, of the 

 opening presents the aciculi beautifully developed (which is also the 

 case at the upper side, at d), standing out from the surface of the ser- 

 pentine, and distinctly separated. Following the aciculi upwards and 

 to the left, they gradually become less distant from one another ; and 

 finally pass into the compact state at c, where it is impossible to observe 

 the smallest openings between them, each being defined by nothing more 

 than its own bounding surfaces, exactly as are the fibres of asbestos. \ 

 On the opposite side, the aciculi are for the most part standing apart. 



Viewing the separated aciculi by themselves, they may be consi- 

 dered to closely resemble the " minute projections" or casts of pseudo- 

 podial tubuli which Dr. Carpenter has noticed on the siliceous 

 "chamber casts" of specimens of Amphistegina, dredged by Professor 

 Jukes oif the coast of Australia : but to believe that the two cases are 

 identical, when in the former the aciculi are plainly seen to graduate 

 into a state which completely excludes the possibility of their being 

 casts of wall-enclosed tubuli, the imagination requires to have more 

 play than can be allowed in a matter-of-fact discussion. 



* The section from which the figure has been taken did not, when it came into our 

 hands, exhibit with sufficient clearness the different " eozoonal features," though quite as 

 well as any other " thin transparent sections ;" so we were induced to decalcify it. 



f The fibres, c, erroneously appear in the figure as if slightly separated. 



