46 PLATYCRINrDiE DICHOCRINUS. 



Synonymes and Reference's. 



Platycrinus elongatus. (interscapular variety). — Phill. Geo/. lo/7i;. PL III. fig. 2Q. 

 Platycrinites laevis. {variety).— M\\\. Crinoid. p. 114. fig. 4. 5. 



Dichocrinus radiatus. — Munst. Brit. zur. Petref. 1. p. 2. 



PI. I. fig. 3, a, b,c,d. 

 Kon. Descr. des Ani. Foss. t. E. 

 fig. 6, a, b, c, d. 



Formation and Localities. 



Carboniferous limestone. — Bolland; Black Rock, banks of the Avon, Bristol; Mendips; 

 and Belgium. 



M. L. De Koninck gives the figure of another species of Dichocrinus, which he terms 

 Septosus, but of which he appears doubtful, as to its appertaining to the genus. The 

 specimens hitherto obtained are not such as to justify us in considering tliis species as 

 established, we therefore omit it. 



M. Koninck states that the columnar canal is pentagonal, in this genus, and the 

 plates in the D. radiatus granulated. The latter is probably the effects of weathering. 

 If not, M. Koninck's must be a different species to that which we have referred to his 

 D. radiatus. 



Though M. Koninck considers it necessary to change the name of Mr. Gilbertson's 

 P. elongatus (Phill. Geo. York.) to that of Dichocrinus, we are confident the species 

 established by the last named Author is a good one, and therefore to be retained, for 

 there is an elongated crmoid with an undivided dorso-central plate, and with five 

 perisomics restmg on it. This is represented in our second iilate fig. 2,g, h. 



The difficulty has occurred through uniting those specimens with six perisomic plates, 

 and a bipartite dorso-central plate, with those which are clearly Platicrini. 



