T TI E V NNALS 



A NT. 



MAGAZINE OF NATURAL HISTORY. 



[THIRD SERIES.] 

 No. 95." NOVEMBER 1865. 



XXXIII.— On the Microscopic Structure of the Shell of Rhyncho- 

 nella Geinitziana. By William B. Carpenter, M.D., F.R.S , 

 F.L.S., F.G.S. 



In consequence of my prolonged absence on the Continent, it 

 has been only within the last few clays that I have seen Prof. 

 King's " Remarks on the Histology of Rhynchopora Geinitziana," 

 contained in the Ann. Nat. Hist, for last August (p. 124). These 

 remarks have led me to subject my preparations of that shell to 

 a renewed microscopic examination, of which I have now to 

 state the results. Before doing so, however, I may say that I 

 have done my best to dismiss from my mind any prejudice in 

 favour of that view of its structure which I might be supposed 

 to derive from the conclusion to which I had been led by my 

 previous researches — that whilst the perforation of the shell by 

 canals passing from surface to surface is the family character of 

 the Terebratulida, the absence of such perforation is the family 

 character of the Rhynchonellidce. The progress of natural-his- 

 tory inquiry is continually bringing to light examples in which 

 features essentially characterizing one group appear in particular 

 types belonging to another. Thus, a paper " On Rose-spored 

 Mushrooms," by Mr. Berkeley, now lying before me, commences 

 as follows :— " I have already pointed out that a single species 

 with decidedly rose-coloured spores (Agaricus euosmos) occurs in 

 the white-spored series; but its affinities with the common 

 Oyster-Mushroom {A. ostreatus) are so intimate that it would be 

 in direct opposition to nature to separate them." It would not 

 in the least surprise me, therefore, to meet with a perforated 

 Rhynchonellid ; and I cau honestly say that no ivish to make 

 out Rhynchonella Geinitziana imperforate is father to the belief 

 that, as regards its outer layer, it really is so. 



The preparations in my possession consist (1) of transparent 

 lamellae, scaled off from the exposed surface of German and 



Ann. ty Mag. N. Hist. Ser. 3. Vol.-a.vi. 21 



