OCULAR AND GENITAL PLATES. 



105 



and here consider the several forms from the Pacific and Atlantic as all referable to C. setosus. 

 In this species we find most interesting characters in regard to oculars, for the phases seen as 

 stages in development and variation in the adult cover the whole range of characters seen in 



in 



Text-figs. 81-87. — Ocular plate arrangement in Mesozoic Centrecliinidae. 



8L Pseudndiadcma pseudodkidcma (Lamarck). Coral Rag, Yonne, France. Diani. 20 mm. R. T. J. Coll., 716. 

 X 8. All oculars insert, typical character. 



82. The same. Corallien, Troviville. G. Boehm Coll., Freiburg i. B. X 4. Ocular I insert, a progres.sive variant. 



83. Magnosia pundulata (Lamarck). Oxford, Berner Jura. G. Boelmi Coll., Freiburg i. B. X about 20. AH 

 oculars cxsert. 



84. Phymcchinus 7nirabilis Agassiz. Oxford, Berner .Jura. G. Boehm Coll., Freiburg i. B. X 4. All oculars exsert, 

 typical character. 



8.5. Stomechinus bigi-anidaris Lamarck. Inferior Oolite, Broad Windsor, Dorset. Diam. 47 nun. R. T. J. Coll., 721. 

 X 4. All oculars exsert, typical character. 



86. The same. Diam. 48 mm. R. T. J. Coll., 715. X 4. Oculars I, V insert, a progressive variant. 



87. Orlhopsis miliaris (d'Archiac). Cretaceous, Les Tamarins, Algiers. Diam. 20 mm. R. T. J. Coll., 717. X 8. 

 All oculars exsert, typical character. 



the fossil and recent members of the family. In a very young specimen (text-fig. 88) all the 

 oculars are fully exsert and this early stage may be compared with the adult Jurassic Pseudo- 

 diadema (text-fig. 81). In an older specimen (text-fig. 89) the oculars are still all exsert, but 



