IN PALEONTOLOGY. 167 



use of oblique illumination, to show their fine markings. Cop- 

 rolites in section reveal with certainty details in the menu of 

 ancient feasts, and in sections of worm-eaten coniferous wood 

 coprolites of the smallest size have been found. 



Dr. Carpenter has investigated a great number of the shells of 

 Brachiopoda, and made out, by careful microscopical examination 

 of transparent sections, a number of interesting and valuable 

 details relating to their structure, the arrangement and markings of 

 their prisms which form the shells ; and the presence or absence, 

 in the various groups, of the curious canals which penetrate the 

 whole thickness of the shell. These canals (so far as yet known) 

 exist in all true TerebratididcB, and are equally wanting in all true 

 RhyiichoiiellidcB^ but in other groups they exist in some species 

 only, and not in others. 



Many of the shells of the Brachiopoda — e.g.^ Porambonites reti- 

 culata — have punctations, but no canals, though on external exa- 

 mination the decided and regular pitting of the surface of this 

 shell closely resembles the large punctations caused by the open- 

 ings of the canals in some of the Terebratididce and Spiriferidce. 



Dr. Carpenter has also shown how the shells of brachiopods 

 differ from ordinary bivalves in their whole shell-structure, corres- 

 ponding to the outer layer only of Lamellibra?ichiata^ being, in 

 fact, calcified epidermis, like the prismatic external layer of Pinna 

 or AviciUa; and so characteristic is their structure, that even 

 minute fragments may be referred with certainty to this group, 

 provided metamorphic action has not altered their minute struc- 

 ture, as only too frequently occurs. Many shells are of course so 

 minute that they have to be magnified for their forms to be exa- 

 mined ; but many small shells have very fine markings, or spines, 

 and even in a few cases minute impressions from the former soft 

 parts of the mollusc, whilst some comparatively large shells have 

 their ornamentation arranged in a minute pattern. 



Leaving out entirely many classes whose investigation has 

 received aid from the microscope, Corals may be noticed as 

 instances in which sections have done so much, and the beautiful 

 arrangement of septa and tubulce demonstrated, and mural pores 

 shown, and other details of the calices made out. 



Sponges, again, have of late been the subject of much micro- 



