A MONOGRAPH OF THE EXISTING CRINOIDS 



121 



milleri 

 Perisorae of the disk with scattered warts, 

 supported by groups of diverging spicules. 



Centrodorsal uniformly convex, and entirely 

 covered with cirri. 



natural history of the European seas pubhshed after his death all these forms are again 

 united under the name rosacea. 



Dujardin in 1862 recognized petasus, from the coasts of Norway, and mediterranea, 

 from the Mediterranean and the western coasts of Europe which are warmed by the 

 Gulf Stream. 



Two British species were admitted by Norman (1865) on the authority of Sir 

 Wyville Thomson; the characters of these were given as follows: 



rosaceus 

 Perisome of the disk naked, or with scattered 

 tubercles containing groups of radiating 

 calcareous spicules. 



Centrodorsal convex, flattened at the apex, 

 its sides covered with cirri, but the central 

 flattened portion, of greater or lesser extent, 

 naked. 



Cirri with 14-18 short segments, the longest 

 but little longer than broad; terminal claw 

 sharp and curved; penultimate segment with a 

 short pointed opposing tubercle, which is not 

 developed into a claw. 



Proximal pair 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 of usually 3 perisomic interradial 

 plates in the spaces between the IBr axillaries. 

 Crimson, scarlet, or mottled. 

 Average diameter iyi inches. 



W. B. Carpenter wrote (1866) that none of these characters seemed to him sufficient 

 for the differentiation of the two species to which they are respectively assigned, save 

 the form of the ovaries which, as he was assured by Wyville Thomson, constitute a 

 strongly marked feature in each, and is not Uable to gradational variations hke size, 

 color, the form and relative abundance of the perisomic plates, or to vai'iations connected 

 with grade of development. He was in doubt as to the proper disposition of the various 

 forms which from time to time had been distinguished. Regarding these he says that 

 he is not able to speak with the positiveness he coidd desire, since his investigations, 

 though prosecuted over a considerable geographical range, had not yet satisfied him 

 as to the limits of variation within this species. In this, as in many sunllar cases, points 

 of difference which seem extremely well marked when the most divergent examples 

 from remote localities are compared are foimd to present gradational modifications 

 which go far to destroy their value as specific characters when a sufficiently large 

 number of examples from intermediate localities are examined. 



He remarks that this will be found especially to be the case with those which rest 

 on degree of development. Thus he can attach little value to the flattening of the 

 centrodorsal in one form and its convexity in another, or to the nakedness of the flat- 

 tened portion in the former while the whole surface is covered with cutI in the latter, 

 when he finds that in the early stage of both the centrodorsal is uniformly convex and 

 entirely covered with cirri so that young specimens of the two could not be differen- 



Cirri with 15-18 segments, the longest half 

 again as long as broad; terminal claw curved 

 and acute; no trace of an opposing spine. 



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 occupying the 



spaces between the IBr axillaries. 



Rich brown or reddish tawny. 

 Average diameter 11 inches. 



