144 



As will be gathered from the statistical tallies given in this 

 paper, the fauna of Cleveland, both recent and fossil, is a 

 very rich one. nearly four thousand species having been 

 recorded. This richness is primarily due to the great variety 

 of natural habitats the area p — -- - each one of which'is 

 inhabited by a special suite of animals. For not only is 

 there a varied coast-line with sheltered bays, low sandy shores. 

 a tidal estuary, precipitous cliff's, and long stretches of inter- 

 tidal scars ; but there is likewise a varied land surface with 

 lulls and valleys, woods and moors, swamps and streams. 

 To the residents have also to be added the animals which 

 visit these localities, either as regular immigrants, casual 

 visitors, or as accidental introductions by man. On turning 

 to the rocks of the district we find that they contain a areat 

 suite of organic remains, numbering over a thousand species 

 occurring in groups in the different strata, and now all 

 extinct. 



Regarding this fauna as a whole we shall deal with it from 

 two standpoints, the statical and the dynamical. The 

 statical aspect treats of the fauna as it is at present, its 

 species and their local distribution, its divisions into natural 

 groups or associations, and the likenesses and differences 

 of these groups as compared with one another, and to similar 

 and dissimilar groups in this and other count! 



Th: dynamical aspect of the fauna treat- of the history 

 of the animals which have lived within the district and their 

 origin : the lines of past migration and distribution, and the 

 changes the fauna lias undergone in relation to past climates. 

 and past vicissitude's of geography. In other words, it deals 

 with the evolution of the fauna, and the causes which have 

 contributed to that evolution. 



It will be convenient to consider first the present marine 

 fauna, to see of what species it is composed, and their status on 

 the district coast-line. Unfortunately, it will not be possible 

 to treat of the divisions of the marine fauna into groups or 

 associations, corresponding with the different habitats of 

 the different species, since few observations except those of 

 a very general kind have been made on this subject. 



We shall next pass on to the history of the marine animals 

 of the Cleveland coast, and ascertain the period when they 

 entered the district. We shall then discuss the past marine 



