396 G. Hickling — Old Red Sandstone of Forfarshire. 



allied. We find probable agreement in such points as the apparent 

 division of the head-region into two segments as by the ' cervical 

 groove ' in Anaspides. Such differences as have appeared are readily 

 explicable as comparatively unimportant differentiations which might 

 be expected to occur within the limits of the group, or as due to the 

 present imperfect state of our knowledge of the fossil forms. We 

 conclude, therefore, that Anaspides is to be regarded as the repre- 

 sentative of a group of primitive Malacostraca, which had already in 

 Palgeozoic times attained a certain degree of specialization and a very 

 wide distribution." 



The pala3ozoologist naturally expects to meet with more generalized 

 and primitive types of structure among the early forms of life discovered 

 in the Palaeozoic rocks, but he less frequently hopes to find actual 

 representatives of these ancestral forms surviving at the present day. 

 When such is the case, however, these persistent forms have a more or 

 less worldwide distribution, there being apparently always a corre- 

 sponding amplitude of measure between the length of past geological 

 time during which a type has existed and its present geographical 

 distribution. 



Take, for instance, the ' king-crabs ' (Xiphosura), we have evidence 

 of their existence from the Upper Silurian to the present time, and 

 they attain the same wideness in their life distribution now. The 

 Scorpionidse also enjoy equal geological antiquity and even wider 

 modern geographical extension. 



The common ' River Cray-fish,' Astaciis Jluviatilis, with its 

 marvellous worldwide distribution,^ had its undoubted representatives 

 in the Chalk, Jurassic, and Trias, which in turn derived their origin 

 from the more generalized forms of Anthrapalsemonidse of the Coal- 

 measures. 



After the discovery by G. M. Thomson of Anaspides living in 

 freshwater pools on Mt. AVellington, Tasmania, at an elevation of 

 4,000 feet above the sea, and of Koonunga cursor by 0. A. Sayce 

 near Melbourne, Australia, we may probably learn of the existence of 

 similar persistent simple congeneric Schizopod-like forms in the fresh- 

 waters of remote and widely separated parts of the globe, just as we 

 know of their past life-history in the widely distributed Carboniferous 

 strata of Britain and the continents of Europe and America. 



II. — The Old Ked Sandstone of Foefakshiee, Upper and Lower. 

 By George Hickling, B.Sc, Lecturer in Geology in the University of Manchester. 

 (PLATES XX AXD XXI.) 

 Introduction. 



DURING the past ten years I have spent much time on the cliffs 

 of the Forfarshire coast, and to the magnificent sections of the 

 Old Red Sandstone therein displayed I owe very largely my interest in 

 geology. In the neighbourhood of Arbroath the well-known uncon- 

 formity between the upper and lower members of that series is admirably 



1 See "The Cray-fish," by T. H. Huxley, F.R.S. (18S0), pp. x and 372, with 

 82 illustrations. Kearan Paul & Co. 8vo. 



