472 Mr. C. B. Clarke. [Feb. 25, 



mens demonstrate the exact features of these structures. Professor 

 Bertrand, of Lille, and M. Hovelacque, of Paris, have simultaneously 

 investigated the two lateral points on the leaf-scar, to which the 

 former author has given the name of parichnos, which name Pro- 

 fessor Williamson adopts. But these two palaeontologists have 

 further called attention to a fourth structure in these leaves, hitherto, 

 in some degree, overlooked ; and which they designated the ligule. 

 The author finds this organ well developed both in L. Harcourtii 

 and in Lepidophloios, but rejects the name ligule, on the ground 

 that he cannot identify the fossil structure with the organ bearing 

 the same name in living Isoetes and Selaginellee. He, therefore, 

 adopts for the former the term Adenoid organ, believing it to have 

 had glandular functions. Details are also given of the organisation 

 of several forms of Lepidostrobi, some of which are identified with 

 their parent plants. 



The general conclusion arrived at by the author in reference to 

 the L. Harcourtii, which has been so often made the subject of 

 debate during the last twenty years, is that it occupies no exceptional 

 position amongst the other Lepidodendra, but that whilst palaeon- 

 tologists in various parts of the world quote the species as one with 

 Ihe organisation of which they were familiar, they were all alike mis- 

 taken in their determinations. Until now no specimen of the same 

 plant has been in the possession of any observer less imperfect than 

 that described by Brongniart; hence, when in the past authors have, 

 as was my own case, referred various examples of cortex, leaves, and 

 fruits to Lepidodendron Harcourtii, we have no evidence whatever 

 that such references are true ones. 



If such references are still declared to be authoritative, I must ask 

 where the specimens are to be seen that carry our knowledge beyond 

 what we derived from Harcourt's imperfect branch. 



IV. " On Biologic Regions and Tabulation Areas." By C. B. 



CLARKE, F.R.S. Received February 8, 1892. 



(Abstract.) 



Biologic regions have been used for two purposes, viz. : (1) to ex- 

 hibit the most natural primary divisions of the globe, so far as the 

 distribution of existing Mammalia (or of plants or living things) is 

 concerned ; (2) as areas of reference on which the complete distribu- 

 tion of a large genus or order of plants or animals may be tabulated. 



It is clearly of the highest importance that one set of areas of 

 reference should be employed by all naturalists, as foreseen by Mr. 

 Wallace when he devised his primary zoologic regions and sub-regions. 

 If one naturalist tabulates one order of Butterflies on one geographic 



