64 



But the establishment of the genus syphon'ia, it is hoped, 

 will considerably assist in the required arrangement of 

 this class of fossils : the obvious tubular structure in the 

 fossils of this genus will readily enable the student to effect 

 their separation from those of spongia and alcyonium : and, 

 in consequence of this abstraction, it will in future be only 

 required to determine to which of these two genera the re- 

 maining ambiguous fossils of this class are to be attached ; 

 or failing in this, to endeavour to detect in them the cha- 

 racters of some undescribed genus. 



With respect to the ascertaining of the stratum, or even 

 the formation, to which the alcyonic fossils belong, little 

 more than negative information can be given. It does not 

 appear that they exist among the syphonia in the green 

 sand : none having been spoken of as existing in the rich 

 mines of Warminster, in the Portland freestone, or in the 

 Black-down hills of Devonshire. 



Some fossils, which have been considered as belonging 

 to this genus, have possessed appearances which led to the 

 suspicion that they had been imbedded in some of the 

 strata of oolitic formation ; but no positive evidence has 

 been adduced of their having been found in such situations ; 

 nor do any statements appear to have been made of their 

 remains having been detected in any of the subjacent form- 

 ations of Ijas, mountain limestone, Szc. 



It is from the examination of the matrix of some fossils 

 apparently of this genus that the conjecture is offered that 

 the chalk marie is the stratum to which the alcyonia more 

 peculiarly belong. 



Tethia. — A tuberous, subglobose polipifer ; fibrous within ; 

 the fibres rather fasciculated ; divaricating or radiating from 

 the centre to the periphery, and glued together by a small 

 portion of pulpy matter ; cells in a cortical crust disposed 

 to fall off. 



