DEVELOPMENT OF AJNfTEDON (COMATULA, LAMK.) EOSACEUS. 695 



Synonymy. 



6. Eefening to the memoir of the Rev. A. M. Norm.\n " On the Genera and Species 

 of British Echinodermata " ' for definitions of the Order Ciunoidea, the Family Ante- 

 DONID.E, the Genus Antedon, and the Species rosacciis, I have now to state my views on 

 its synonymy. As to this I am not able to speak with the positiveness 1 could desire, 

 since my investigations, though prosecuted over a considerable Geographical range, have 

 not yet satisfied me as to the limits of variation in this type. In this, as in many similar 

 cases, points of difference which seem extremely well marked when the most divergent 

 examples from remote localities are compared, are found, when a sufficiently large 

 number of examples from mtermediate localities are examined, to present gradational 

 modifications which go far to destroy their value as specific characters. And this will 

 be found especially the case with those characters which rest on degree of development. 

 Thus I can attach little value to the flattening of the Centro-dorsal plate {^ 22) in one 

 type, and its uniform convexity in another, — or to the nakedness of the flattened portion 

 in the former, whilst the whole surface is covered with dorsal cirrhi in the latter ; — when 

 I find that in the early stage of both, the centro-dorsal plate is uniformly convex and 

 entirely covered with dorsal cirrhi, so that young specimens of the two could not be dif- 

 ferentiated. Nor can I adopt as characters of specific difference such variations in the 

 number of Dorsal Cirrhi, the number of their joints, the proportion of the length of these 

 joints to their breadth, and the form of their terminal claw, as I occasionally meet with 

 among the cirrhi of specimens from the same locality resembling each other in all other 

 respects ; the shedding and renewal of these cm'hi continuing, in my opinion, through 



' The following are given by Mr. Norman (Annals of Natural History, 3rd Series, vol. xv. p. 102) on the 

 authority of Professor "Wyville Thomson, as the diagnostic characters oi Antedon rosacetts: — " Perisom of the 

 disk naked, or with scattered tubercles containing groups of radiating calcareous spicules. Centro-dorsal plate 

 convex, flattened at the apex, its sides covered with dorsal cirrhi ; but the central flattened portion, of greater 

 or less extent, naked. Cirrhi 14-18-jointed ; the joints short, the longest but little longer than broad. Ter- 

 minal claw sharp and curved ; penultimate joint with a short pointed opposing tubercle, which is not developed 

 into a claw. Proximal pairs of pinnules at least twice as long as those succeeding. Ovaries short and rounded. 

 Usually, when mature, without any trace of interradial plates ; frequently, however, with groups usually of 

 three perisomatic interradial plates in the spaces between the radial axiUaries. Colour crimson, scarlet, or 

 mottled. Average size 4| inches from tip to tip of arms." — Of Antedon MiUeri the follo^ring are given as 

 characters : — " Perisom of the disk with scattered warts, supported by groups of diverging spicules. Centro- 

 dorsal plate uniformly convex, and entirely covered with dorsal cirrhi. Cirrhi 15-18-jointcd ; the longest of 

 the joints about once and a half as long as broad. Terminal claw curved and acute ; penultimate joints without 

 a trace of an opposing process. Proximal pinnules greatly longer than those succeeding them. Ovaries long 

 and narrow, extending over more than half the length of the pinnules. Groups of interradial plates occup}-ing 

 the spaces between the radial axUlaries. Of a rich brown or reddish-tawny colour. Average size 11 inches 

 from tip to tip of the arms." — None of these characters appeal- to me sufiicient for the differentiation of the two 

 species to which they arc respectively assigned, save the form of the ovaries, which (as Professor WrviixE 

 Thomson assures me) constitutes a strongly marked feature in each, and is not liable to gradational variations 

 like Size, Colom-, the form and relative abundance of the Perisomatic plates, or to variations connected with 

 grade of development like others uUuded to above. 



IIDCCCLXVI. 5 C 



