350 ECHINOBRISSUS 



evident. Between the newer Portland species, U. Brodeii, Wr., and E. scutatus, a detailed 

 analysis will be given in the section on that species. 



Locality and StratigrapMcal position. — I have collected IE. scutatus, Lamk., from the 

 Lower Calcareous Grit at Bullington-Green, near Oxford, where it was associated with 

 Cidaris Smithii, Wright. I have discovered it was from this same quarry that the 

 large type-specimen of the Cidarite figured in our PI. II was obtained. I have gathered 

 it from the Lower Calcareous Grit at Filey Brig, Gristhorpe Bay, and Scarborough Castle 

 Hill, Yorkshire, and from the same formation at Marcham, and Faringdon, Berks. The 

 Yorkshire specimens I chiseled out of blocks containing Fygurus pentagonalis, Phil., and 

 other Calcareous Grit shells, and the Berkshire specimens were associated with Cidaris 

 Jlorigemma, Phil., and Hemipedina MarcJiamensis, Wright. I have collected it from the 

 CoraUine Oolite at Calne, Wilts, where it is very abundant in some beds. In one slab, 

 about nine inches square, obtained from a large quarry near the town, there are 

 about fifty specimens, more or less imperfect, closely laid together. Like other urchins, it 

 appears to have been gregarious, and would be found in great numbers if its head zone 

 was exposed. Cidaris jlorigemma, Phil., Hemicidaris intermedia, Flem., Acosalenia decorata, 

 Haime, Pseudo-diadema versipora, Phil., lie with it in the same slabs. 



My friend, Charles Pierson, Esq., collected this species from a Pisolitic Oolitic rock — 

 the Lower Calcareous Grit of English geologists — about one mile from Trouville, Calvados, 

 where it is very abundant, and in a good state of preservation. M. Desor states that it is 

 found in the Oxfordien of Trouville, and Vaches-Noires, Calvados, Lannois, Ardennes, and 

 Chamsol, Doubs. 



History. — The history of this species has been already so fully detailed in my analysis 

 of its synonyms, that it is unnecessary to enter into any further details on the subject. 



ECHINOBRISSUS DIMIDIATUS, PMlUps. PI. XXVI, fig. 3 a, b, c. d. 



Clypeus DIMIDIATUS. Phillips, Geology of Yorkshire, pi. 3, fig. 16, p. 127, 1829. 



NxJCLEOLiTES DIMIDTATA. Desmoulins, Etudes sur les Echinides, Synonyme Generale, 



No. 25, p. 362, 1836. 



— DIMIDIATUS. Agassiz, Prodrome d'une Monogr. des Radiares, p, 9, 1837. 



— PARAPLESIUS. Agassiz, Catalogus Systematicus, p. 4, 1840. 



— DIMIDIATUS. Morris, Catalogue of British Fossils, p. 55, 1843. 



— — Agassiz and Desor, Catalog. Raisonne des Echinides Annales des 

 ' Sciences Naturelles, 3° serie, tome vii, p. 154, 1847. 



— DIMIDIATA. Bronn, Index Palseontologicus, p. 818, 1848. 



— DIMIDIATUS. Forbes, Memoirs of the Geological Survey, decade 3, description 



of pi. ix, 1849. 



— — D'Orbigny, Prodrome de Palcontologie, tome 1, p. 379, 1850. 



