ECHLNODEKMATA 29 



Bryozoa, mingled with Foraminifcra. The coralline crag of 

 Suffolk takes its name from the great abundance of Bryozoa it 

 contains, among which Eschar a, CeUcpora, Fascicularia, Theo- 

 noa, Hornera, Idmonea, Flustra, and Tubulvpora are the most 

 important. 



Class IV.— ECHINODEKMATA. 



(Star-Fishes, Sea- Urchins.) 



Char. — Marine ; commonly free, repent animals, with the 

 integument in most perforated by erectile tubular ten- 

 tacles, hardened by a reticulate deposit of calcareous 

 salts, and in many armed with spines. 



The fossil Eadiata present a mine of comparatively unex- 

 hausted riches to the palaeontologist. More difficult of study 

 than shells, and less uniformly present in all strata, the 

 enduring remains of echinoderms and corals are unsurpassed 

 in beauty of form and structure, and in the value of the evi- 

 dence they afford. 



The present summary of the extinct forms of Echinoder- 

 mata will commence with 



Order 1. — Crinoidea. 



Char. — Body with ramified rays, supported temporarily or 

 permanently on a jointed calcareous stem ; alimentary 

 canal, with mouth and vent, both, as in Bryozoa, 

 approximated. 



The " stone-lilies," or crinoid star-fishes, formed a nume- 

 rous and important group in the palaeozoic seas, where they 

 obtained their maximum number and variety. M. d'Orbigny 

 describes thirty-one palaeozoic genera, two triassic, ten oolitic, 

 and four cretaceous — of which latter three (Pcntacrinus, Bour- 

 (fu-cticrinus and Coma-tula) are found in the tertiaries and mo- 



