240  Correspondence—UM. C. Lapworth and C. Stewart. 
perfect kind which characterizes slates and shales. I would, there- 
fore, restrict the term ‘‘schistose”” to an imperfect or irregularly 
fissile structure. Jn this respect I take it that a schist differs from a, 
shale. The definitions of such closely-allied terms must, however, 
depend upon preponderance of evidence concerning the special and 
distinct senses in which they have been employed. Their correct 
application, therefore, is essentially based upon usage. 
Frank Rvutey. 
LINNARSSON’S RECENT DISCOVERIES IN SWEDEN. 
Str,—I have to thank Messrs. Linnarsson and Nathorst, of the 
Swedish Geological Survey, for kindly suggesting the following 
corrections of my paper on “ Linnarsson’s Recent Discoveries in 
Sweden,” as published in the January and February parts of the 
GrotocicaL Macazine for the present year. 
Page 34, line 35. For Murchisoni-bed read Phyllograptus Zone. 
Page 35, line 28, etc. Retiolites Beds. This term is restricted by the Swedish 
geologists to the strata denominated by myself the Zone of Cyrtograptus Murchisoni. 
Page 36, line 9. For highest Silurian strata in Scania, read highest Graptolitic 
strata in Scania. 
Page 68, line 6 from bottom. For regarded as distinct vead regarded as identical. 
Page 70, line 15. Dr. Nathorst was not responsible for the original reference of 
Conocoryphe exsulans, Linnars., to Cono. coronatus, Barr. _He merely adopted the 
identification previously made by Messrs. Lundgren and Linnarsson (Geol. Féren. 
Forhand. 1876, Band ii. No. 9, p. 3, note). 
Sr. ANDREWS, April 19th, 1880. Cuas. Lapworts. 
THE MICROSCOPIC STRUCTURE OF ATELEOCYSTITES.! 
Str,—I have examined by vertical and horizontal sections the 
shells of <Ateleocystites, of Marsupiocrinites, and of the Trilobite 
(Calymene), all from the Wenlock Limestone, Dudley, which you sent 
me. That of Ateleocystites does not show under the microscope the 
normal calcareous network which is so fairly constant in the Echino- 
dermata; but the undoubted Hchinoderm, MMarsupiocrinites, was 
identical in all respects with the former genus.- This I attribute to 
extreme metamorphic action. However, one must not lose sight of 
the fact that the network structure might, even in the living animal, 
have been disguised by its interstices being filled with carbonate of 
lime, a condition often found where there is friction between parts 
(e.g. between head of spine and tubercle, etc.), and to a certain 
extent probably in old parts (e.g. the basals of old Pentacrinites). 
The Trilobite showed the ordinary tubular structure found in the 
thicker-shelled Crustacea. It is evident, from the above, that the 
apparent absence of the calcareous network in Ateleocystites does not 
invalidate its being an Echinoderm. C. Stewart. 
Sr. Tuomas’s Hosprran, Mepican ScHoot, 
ALBERT EMBANKMENT, Lonpon, S.E., April 23rd, 1880. 
1 This note was unfortunately received by the Editor too late for insertion at 
p. 200 ante, where it should have appeared. 
Erratum—In Dr. Callaway’s letter, April, 1880, p. 188, last line, for as read ws. 
