252 On tlie Morpliology of the Blastoldea. 



the peristome and form a kind of spm-ious spiracle ; this is 

 particularly noticeable in 0. stdh'formis. The lancet-plate 

 appears to be exposed in all the species in its u])per part; but 

 towards the distal extremity the side plates meet in the middle 

 line and close over it, the amount of covered surface varying* 

 according to species. 



The side ]ilates are very numerous in O. injJafus and 0. 

 pentangulan's ; but the state of preservation of our specimens 

 does not permit of the actual number being ascertained. 0. 

 steliiformis is said to possess fifty; and twenty-two exist in 

 0. gracilis. There are at least twenty-five in 0. Waier- 

 lioiisiaims, and something under twenty in 0. Orhignyaniis. 

 The hydrosplres, so far as we are acquainted with them, vary 

 from ibur to eight. There are five in 0. sfcllifbrviis, from 

 seven to eight in 0. ivflahis and O. jx^ntanguJaris^ and at 

 least four in the two Belgian species. 



We have not observed in either of the European species a 

 plated ])eristome as described by Dr. C. A. White* ; but we 

 entertain little doubt that it existed in the perfect form. 



The following are the species we refer to Orojiiliocrinus : — 



Codonites gracilis, M. & W. Burlington group (Sub- 

 carboniferous), Iowa. 



Pcniremites ivjiatus, Gilb. Carboniferous Limestone, 

 England. 



P. Orhigvyanus, de Kon. Carboniferous Limestone; 

 Belgium. 



Plaiycrimis jyenfavgidai'is, Miller. Carboniferous Lime- 

 stone, England. 



Pcnlrouites jmzos, Minister, Carboniferous Limestone, 

 Belgium. 



Codonites steJJiformisj O. & S., sp. Burlington group 

 (Subcarboniferous), Iowa &c. 



Pentrernites Watcrliousianus, de Kon. Carboniferous 

 Limestone, Belgium. 



From the above list it wdll be seen that Oropliocriims is 

 entirely confined to rocks of the Carboniferous ])eriod, occur- 

 ring, hoAvever, in those of Britain, Belgium, and America. 

 It thus has a wider geographical distribution than any of the 

 other genera occurring in Britain, Granatocrinus being as yet 

 unknown on the continent, while the Pentremitidea of Spain, 

 the Eifel, and the American Devonian rocks does not occur in 

 Britain; and PJta nosclusrna of England, Belgium, and S])ain 

 is but very doubtfully recognizable among the American 

 Blastoids. 



* Boston Journ. Nat. Hist. 18(>3, vii. p. 480. 



