166 Mr, W. J. Fuller on the Anatomy of Spiders. 



150 individuals, belonging to six or seven species. In the coal- 

 measures whole beds of hard shale may be split into thick 

 laminsB along the surface formed by the crustacean valves. 



In Jurassic times the Ostracoda have, till quite recently, only 

 been known from a few scattered finds ; but a splendid series of 

 specimens from the fuller's-earth clay has lately been obtained, 

 and these have been described by Professor Eupert Jones and by 

 myself, and fill up an important gap in the geological history of 

 the Ostracoda. 



The immense masses of Cypris limestone and shales of the 

 Purbeck and Wealden formations must be well known to all 

 geologists present. Some of these beds are entirely composed 

 of ostracodal valves, and in the case of at least one form fix the 

 age of the bed with great exactness. In the Wealden area, the 

 paper shales of Shepherd's Chine, Isle of Wight, cannot fail to 

 be noticed by the most casual observer. Here, for foot after foot, 

 the clay-beds may be split up into laminse as thin as paper, the 

 lamination being almost entirely due to the smooth valves of 

 Cypridea valdensis. At Brook Point, in the hard reddish-brown 

 clays, thousands of specimens can be obtained from a few square 

 inches; indeed, the whole of the coast section between Brook 

 and Atherfield, and again at Sandown, offers abundant points 

 where these Ostracoda may be seen as rock formers, and where 

 specimens may be collected without trouble. 



From the Gault and Chalk a large and beautiful series has 

 been described, and before long a revised list, including the new 

 species collected since the first descriptions were pubUshed forty 

 years ago, will soon be ready. 



Nearly every Tertiary clay yields a harvest of Ostracoda, and 

 very considerable thicknesses of the Hempstead beds of the Isle 

 of Wight are thickly crowded with valves of Cytheridea Mulleri, 



72. — The Anatomy of Spiders. 

 By William J. Fuller, F.I.O. 



(Read December 12th, 1888.) 



The spinning spiders (Araneina) are commonly supposed to be 

 insects, but in every important characteristic they differ from the 

 Insecta, and are really much more nearly allied to the Crustacea. 

 The eyes, when present, are two, four, six, or eight, generally 

 eight, and are simple lenses, sometimes very large and bright, 

 and very different from the complex facetted eyes of insects. 

 They are variously situated on the anterior portion of the 



