94 Guide to the Invertehrata. 



Echi- It is a close ally of Phormosoma and Asthenosoma, two living 

 noidea. g^^^ncra which were subsequently found at great oceanic depths. 

 ^^vm^^ The remarkable perignathic girdle of Discoidea shown in a 

 East Side, specimen (40,341) from the Chalk of Burham, resembles that 

 Wall-cases of a small recent West Indian species. The type of Pygurus 

 Tablel lampas (Beche), from the Upper Greensand of Lyme Regis, is of 

 cases interest from its remarkable form, and its rarity, it being the only 



known specimen of the species. 



The series of Echinoids belonging to the genera IFagenovia and 



Infidaster are worthy of attention owing to their abnormal forms ; 



76-78. 



Fio. 151. — Upper surface of Micraster cor-anguinum, Leske. Upper Chalk: 

 Bromley, Kent. 



and the collection of specimens of Echinocorys scutatus (syn. Anan- 

 chytes ovatus) illustrates the varying forms that can be adopted by 

 a single species. 



The British Cainozoic "Echinoidea are fewer in number and 

 smaller in size than those of the Cretaceous and Jurassic periods. 

 The Eocene series contain a few forms which in comparison with 

 those which lived at the same period in Southern Erance are 

 dwarfed and stunted. The Crag species are larger and more 

 numerous. The most interesting species is Temnechinus JFoodi, 

 of which both the male and female forms are shown in the 

 collection ; the latter was originally described as Temnechinus 

 excaiatus. The presence of several sea-urchins of West Indian 

 types, such as Rhynchopygus Woodi, Agassizia equipetala, and 



