Oeneric Position o/'Sola.nocrinus. 83 



Solanocrinus scrohiculatus *^ and I pointed out that it recent 

 Comatulas be divided into two groups, according as they have 

 («) radial pits and a five-lobed axial opening, or {h) no radial 

 pits and an undivided opening, Antedon rosacea ViXidi A. celtica 

 " would appear in both groups, while some individuals with 

 lobate or decagonal openings, but no pits, would find a place 

 in neither." 



The latter condition is an extremely common one ; but 

 radial pits are decidedly rare in recent Comatulee, quite a 

 number of which have a round axial opening on the centro- 

 dorsal without any pits on its margin, just as in Solanocrinus 

 as defined by Walther. 



The only character, then, on which Walther can rely for his 

 revival of Solanocrinus as a genus distinct from Antedon is 

 the supposed absence of any syzygies in its rays and arms ; 

 and he says of every one of his specimens that " Syzygialnahte 

 fehlen." His own descriptions and figures appear to me to 

 show, however, that quite the reverse is the case, and that in 

 the three species which he refers to Solanocrinus we have the 

 predecessors of a very small group of recent forms of Antedon 

 in which the second and third radials are united by syzygy. 



Let us consider first the type species, Solanocrinus costatus, 

 three examples of which are described and figured by Walther. 

 On Taf. XXV. fig. 1 he represents a portion of a ray which 

 consists of the two outer radials with the bases of the two 

 arms that are borne on the axillary. His own descriptionf of 

 it commences as follows : — " Das Stiick beginnt mit dem aus 

 Eadiale II. und Radiale III. verschmolzenen Axillare, welches 

 eine Verwachsungsnath wohl erkennen liisst." But if this 

 " Verwachsungsnath " is not a syzygy, what is it ? It is well 

 shown in Walther's figure on the ventral side of the com- 

 pound axillary ; and a comparison of this figure with the 

 corresponding parts of the recent Actinometra paucicirra 

 (fig.l, B, p. 84) leaves little doubt in my mind that in the fossil, 

 as in the recent type, there is a syzygial union between the 

 two outer radials. In like manner Walther says of another 

 example (of S. costatus) that the second radials " mit dem 

 Radiale III. verschmolzen, aber durch eine Kinne davon 

 abgegrenzt sind." Here again we seem to have distinct 

 evidence that the two outer radials are united by syzygy, just 

 as in many recent Comatul^ (fig. 1, A). Walther says in 

 his specific diagnosis of this type : — " Radiale II. mit Radiale 

 HI. verschmolzen, doch durch eine Nahtlinie getrennt." 

 His non-recognition of this as a syzygial union is the more 



* Loc. cit. p. .34. t Op. cit. p. 171. 



ft* 



