SAGENOCRINIDAE 243 



is founded under my classification, let us now return to the original description by De Koninck 

 and Le Hon of their genus Forbesiocrinus. In addition to the generic formula, they gave 

 not only an elaborate description in the terminology of De Koninck and Le Hon, but a 

 generic diagram (which I have copied on Plate XXII), together with figures and descrip- 

 tion of two specimens. From these it clearly appears that the posterior basal, instead of being 

 truncate and followed by a tube-like series of plates bordered by fragile perisome, is angular 

 above, supporting two anal plates suturally joined to the adjacent brachials and followed by 

 some others. Although they did not dwell upon this character in their discussion of resem- 

 blances and differences, nevertheless the structure as above stated clearly appears in the 

 generic diagram ; and in the diagnosis of " caracteres generiques " it is given as follows : 

 " Ce qui distingue surtout le cote anal des autres, c'est que l'extremite superieure de la piece 

 basale qui y correspond est soudee a deux petites pieces anales et qu'elle porte, par consequent, 

 deux facettes articulaires de plus que les quatre autres pieces basales, dont aucune ne se 

 soude directement aux pieces interradiales " (op. cit., p. 119). 



It is evident from these facts that the genus as proposed by De Koninck and Le Hon is 

 perfectly distinguished from Taxocrinus, and that upon structural grounds alone its validity 

 should be no longer open to question. I have, however, made the above somewhat full 

 extract from their description in order to emphasize the further fact that the structure 

 described and illustrated is totally different from that of Phillips's species Taxocrinus 

 nobilis, under which name they erroneously identified the specimens upon which their generic 

 diagnosis was founded. Considering only Phillips's figure in the Geology, of Yorkshire, 

 plate 3, figure 40, with its one to three small " interradial " plates, and no trace of the inter- 

 axillaries which led the authors to believe the calyx in their genus extended to the last arm 

 bifurcation; and bearing in mind that it represented a large and mature specimen in which 

 interbrachial structures, if present, would be at their fullest development ; — it must have 

 been held, even with the views expressed by De Koninck and Le Hon themselves, to be a 

 very different species ; and it is difficult to understand how so ardent a student of the crinoids 

 as De Koninck could ever have confounded the Belgian specimens with it. 



When in addition to this we examine the type specimen in the Gilbertson collection in 

 the British Museum, which I have refigured after- additional cleaning (PL LIV, figs, ia-c), 

 showing the truncate posterior basal with the clear trace of a facet for the support of a 

 vertical series of anal plates, it must become sufficiently apparent that the identity of 

 De Koninck and Le Hon's genus with the species Taxocrinus nobilis is absolutely negatived 

 by their own description and diagram. And if to these facts we add the further evidence 

 afforded by my new figure of one of the types showing the actual construction of the anal 

 side in the original specimen, and in my own better preserved specimens, the above con- 

 clusion becomes irresistible. As if to make assurance doubly sure, I received from M. Piret 

 after the foregoing paragraph was written an additional piece of confirmatory evidence in 

 the shape of a good specimen of an unquestionable Taxocrinus from the same beds at 

 Tournai, the first one ever found (PL LIV, figs. 2a, b). It shows that the two genera existed 

 side by side in the Tournai limestone ; and if De Koninck had had this specimen in hand he 

 would never have confused his others with Phillips's species. 



We may therefore take this fact as proved, viz., that the Belgian type upon which 

 De Koninck and Le Hon founded their genus is not identical with the English species of 

 Phillips to which they referred it; or, in other words, that Forbesiocrinus nobilis De Koninck 

 and Le Hon and Taxocrinus nobilis Phillips are two entirely different species. 



With this proposition established, we are in a position to consider the question of the 

 validity of the name Forbesiocrinus. As to this two courses are open, for each of which 

 good arguments can be given : 



1. De Koninck and Le Hon established the genus on Phillips's Taxocrinus nobilis as 

 the type and only species. This has the characters of Taxocrinus and must remain in that 



