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



Synoxtmt. 



6. Referring to the memoir of the Rev. A. M. Nobmax " On the Genera and Species 

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

 DONiD^, the Genus Antedon, and the Species rosaceus, I have now to state my \-iews 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 intermediate 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 cirrhi continuing, in my opinion, through 



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

 authority of Professor "Wyvillb Thomson, as the diagnostic characters of Antedon rosaceus : — " 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 intcrradial plates ; frequently, however, with groups usually of 

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

 mottled. Average size 4| inches from tip to tip of arras." — Of Antedon MiUeri the following are given as 

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

 dorsal plate imiformly convex, and entirely covered with dorsal cirrhi. Cirrhi 15-18-jointed ; 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 intcrradial plates occupying 

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

 from tip to tip of the arms." — None of these characters appear to me su£5cient for the difierentiation of the two 

 species to which they are respectively assigned, save the form of the ovaries, which (as Professor Wyville 

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

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

 grade of development like others alluded to above. 



JIDCCCLXVI. 5 c 



