INVERTEBRATE FOSSILS OF THE BURLINGTON GROUP. 



RADIATA. 

 ECHINODERMATA. 



CRINOIDEA. 

 Genus DICHOCRINUS, Miller. 



Synon. — Platycrinus (var.), Miller, 1821. Nat. Hist. Crinoidea, 114; (not ib. p. 74.) 

 Platycrinus (sp.), Phillips, 1836. Geol. Yorks., II; Austin (sp.), 1843, 



Monogr. Crinoidea. 

 Dichocrinus, Munster, 1838. Bietrag. Z. Petref., 1. 

 ? Cotyledonocrinus, Casseday and Lyon, 1859. Am. Acad. Arts and Sci., vol. 



iv, p. 26. 



The generic formula of this group, given by M. M. de Koninck and Lehon, 

 in their valuable " Recherchcs sur les Urinoides du Terrain Carbonifere de Bel- 

 gique" p. 146, is as follows : 



Basal pieces, 2. 



Radial pieces, 4, one of which is large, -4-5. 



Interradial pieces unknown. 



Anal pieces, 1 known, very large, resting on the base. 



Number of arms, 10. 



Since this formula was published, a number of species have been described 

 in this country, some of which seem to show that it should be slightly modi- 

 fied, probably as follows : 



Basal pieces, 2. 



Radial pieces, 2 to 4?-f-5; the first always much larger than theothers. 



Interradial pieces, 4 to 5. 



Anal pieces, 1 to 5; one large and resting on the base. 



Arms, 10, bifurcating. 



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