PLATYCRINID.i:. rLATYCRINITES. 25 



represented in our illustration in the second plate, in all probability appertains to the 

 mucronatHs ; but as our rule is not in any case to refer an unattached fragment to a 

 specimen, unless we are well assured by decided evidence that it really belonged to the 

 individual to which we assign it, Ave hesitate in the present instance to refer the unat- 

 tached fragment to any particular species. 



The Base op Attachment. — Unasccrtamed. 



The lateral mouth, and pecidiar size and arrangement of the plates which cover the 

 \ertex of this species, are sufficient to constitute generic distinction ; but as we are 

 averse to multiply genera, already too numerous in some departments of natural science, 

 we at present retain it in the long established genus Platycrinites. Did we consider it 

 expedient to elevate it to generic distinction, we should take the mucronatus as the tj'pe 

 of our proposed genus PJeurocrinus. 



4. Species. Platycrinites elongatus. (Gilbertson.j 



Defuiition. — -Dorso-central plate conical and pentagonal ; perisomic plates either live 

 or six, and much elongated as compared with others of the genus ; proboscis or oral 

 tube elongated, large, and central ; column, rays and base of attachment unknown. 



Synonymes and References. 



Platycrinites elongatus.— Gilb.—Phill. Geol. York. PL lU.fg. 'i-l, 26. 



— Messrs. Austin, Ann. and Mag. Nat. Hist. vol. 10, p. 109. 



Formation and Localities. 



Carboniferous or mountain Hmestone, Woodspring, Somerset ; Bolland ; Hook Point, 

 Wexford. 



TMs .species is not so numerous, or as extensively diffused as either the P. kevis, or 

 the spinosus. Hitherto only a very Umited number of specimens have been obtained 

 from the mountain limestone of England, and we have only met with a single imperfect 

 indiA-idual m the same formation in Ireland. This fact may be considered as another 

 proof that the limits to the extension of species was as well defined in the earlier ages 

 of our planet, as in our more recent seas. 



E 



