Species of British Echinodcrmata. 101 



the basal joints of the arms united with a calyx-shaped base, 

 which is composed cither of a single calcareous piece or of nu- 

 merous angulated plates closely cemented together. Mouth and 

 anus both superior, and distinct from each other. Respiration 

 (in Antedon) chiefly effected by means of the tentacula which 

 fringe the sides of the arms and pinnules, and the ciliated sur- 

 face of channels which traverse the upper side of the arms. 

 No madreporiform tubercle. Sexes distinct. Ovaries externally 

 conspicuous, attached to the sides of the pinnules or ultimate 

 subdivisions of the arms. 



Tarn. Antedonidae. 



Young animal cemented to stones, shells, or sea-weed by a 

 muitiarticulate peduncle of considerable length, originating from 

 the aboral and inferior calyx-formed side of the body. Adult 

 animal free (a separation having taken place at the junction of 

 the peduncle with the calyx), having the calyx furnished with 

 numerous many-jointed and clawed cirrhi, by means of which it 

 clings at will to Laminarice or other bodies. Arms bifurcating 

 close to the base, beneath the surface of the body, and in some 

 foreign species again and again subdivided; composed of joints 

 which are transversely somewhat wedge-formed, so that they are 

 alternately wider on either side of the arms; each such joint on 

 its wider side gives support to a multi-articulate pinnule. Oral 

 surface of the body covered with a thin membranous skin. 



Genus I. Antedon, Freminville. 



[Antedon, Freminville, 1S11; Alecto, Leach, 1815; Comatula, Lamarck, 



1816.] 



Mouth central. Anus lateral. Calyx or aboral surface com- 

 posed of a single piece, with which the five radial plates of the 

 base of the arms articulate. Arms with two or three basal 

 joints, after which they bifurcate, and in some foreign species 

 are subsequently a second and even third time subdivided. 



We feel that we have no choice. The name of Antedon must 

 be employed in preference to that of Comatula. Fre'minville's 

 genus has five years' precedence over that of Lamarck, and was 

 thus clearly defined (Bull. Soc. Philomatique de Paris, vol. ii. 

 1811, p. 349) : — "Animal libre, a corps discoide, calcaire en 

 dessus, gelatineux en dessous, environne de deux rangs de 

 rayons articules, pierreux, perces dans leur largeur d'un trou 

 central ; ceux du rang superieur plus courts, simples et d'egale 

 grosseur dans toute leur longueur; ceux du rang inferieur plus 

 longs, allant en diminuant de la base a la pointe, et garnis dans 

 toute leur longueur d'appendices altcrnes egalement articules; 



