the Morpliology of the BlastoiJea. 235 



Orophocrinus and Phcenoschismaj which are also devoid of 

 pores at the sides of the ambulacra leading into the hydrospires. 

 But Cadaster is a true Blastoid in every respect ; and we 

 think that Billings was led to this erroneous conception bj 

 his not having emancipated himself from the old doctrine of 

 the pinnules of Pentremites being placed directlj over the 

 hydrospire-pores bordering the ambulacra, a theory now 

 abandoned by all the more prominent writers on the Blastoidea. 

 The following species are comprised in the genus Co- 

 dasfpr : — 



'"Cadaster acutus, M'Coy. Carboniferous Limestone, 

 England. 



C. alternatus, Lyon. Upper Helderberg group (Lower 

 Devonian), Kentucky. 



C. americanus, Shumard. Upper Helderberg group 

 (Lower Devonian), Kentucky. 



C. pi/rainidatnsj Shumard. Upper Helderberg group 

 (Lower Devonian), Kentucky. 

 *C. trilobatus, M'Coy. Carboniferous Limestone, Eng- 

 land. 



C. Whiteij Hall. Burlington group (Subcarboniferous). 



Codaster thus appeared first in the Lower Devonian of 

 North America, and was represented by three species. It 

 extended into the Carboniferous Limestone of the same con- 

 tinent and of the British Islands ; but we believe it to be un- 

 known in the Upper Palaeozoic rocks of the continentof Europe. 



If the Blastoid described by Messrs. Miller and Dyer as 

 Codaster jmlchellus^ belongs to this genus, which we very 

 much doubt, Codaster will then range back in time as far as 

 the Niagara group (Wenlock). 



Codaster Illndei^ sp. nov. 



8p. char. Calyx obtusely conoid and wall-sided j summit 

 more or less truncated and decagonal ; oral crests of nearly 

 equal length with the ambulacra. Basal and radial plates 

 about equal in length, the latter convex, most sharply so in 

 the middle line ; but the limbs are placed at such an angle 

 that the union of every two produces a perfectly flat side to 

 the calyx ; sutures not marked by any dejn-ession j sinus 

 rhombic. Four regular oral plates rhomboid and arched, 

 with a narrow sharp oral ridge, either in the same general 

 plane with the summit or incliricd very slightly outwards, 



* Probably idoutical. 



t Joiini. Oiucinuati Soc. Nat. Hist. 1878, t. ii. f. 13. 



