424 Etheridge and Carpenter — Catalogue of the Blastoidea. 



constructed calyx of any Pelmatozoa, and in fact of any Echinoderms. 

 Under-basals may occur in all the brachiate forms, while the hasals 

 of Crinoids may vary in number from two to five, and the develop- 

 ment of the interradials varies extremely among the different groups." 

 (p. 119.) 



There is a persistent number of thirteen plates in the Blastoids, 

 with the single exception of Elcsacrinus, which has the posterior 

 deltoid divided into two by the anal plate ; and with the exception 

 of three genera, Eleutherocrinus, Astrocrinus, and Pentephyllum, the 



ECHINODERMATA. 





Upper 

 Silurian. 



Devonian. 



Carbon- 

 iferous. 



Branch Pelmatozoa. 

 Class Blastoidea. 



O Qj 



o g_ 



America. 



.8 





C 



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Order Eegulares, E. and C. 



Pentremitid-s:, D'Orb. 



Pentremites, Say 



Pentremitidea, D'Orb 



Mesoblastus, E. and C 



TfioosTOBLASTiDiE, E. and C. 



Troostocrinus, Shumard 



Metablastus, E. and C 



Triccelocrinus, M. and W 



Nucleoblastid-s:, E. and C. 



Elceacrinus, Boemer 



Schizoblastus, E. and C 



Cryptoblastus, E. and C 



Acentrotremites, E. and C 



Granatoblastid^;, E. and G. 



Granatoci inus, Troost 



Heteroblastus, E. and C 



Codasteridje, E. and C. 



Godaster, McCoy 



Ph(snoschisma, E. and C 



Orophocrinus, von Seebach 



Oryptosehisma, E. and C 



Order Irregulares, E. and C. 



Astrocrinidje, T. and T. Austin. 

 Astrocrinus, T. and T. Austin 

 Eleutherocrinus, Shum. and Tand. 

 Pentephyllum, Haughton 



Total 



49 

 18 



7 



2 

 7 

 5 



9 



10 



3 



1 



10 

 2 



15 

 7 

 9 

 2 



2 

 3 

 1 



162 



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