Species of British Echinodermata, 115 



ham ; and Mr. Edward has sent it to us from Banff. It is an 

 inhabitant of the coralline zone. 



Order III. ASTEROIDEA. 



Body stellate or angular, produced into five or more, more or less 

 elongated lobes or hollow arms, or rather rays, which are perfectly 

 continuous with the disk, and contain csecal prolongations of the 

 viscera. These rays throughout the entire length of the oral 

 surface are centrally hollowed into channels, called ambulacra, 

 from which are protruded two or four rows of suckers. Repta- 

 tion by means of these suckers and of others which are situated 

 on the disk. Skeleton composed of numerous calcareous plates, 

 variable in number and size, and supporting a coriaceous enve- 

 lope which is pierced on the aboral surface by pores for the pro- 

 trusion of respiratory tentacles, and bearing for the most part 

 numerous spines. These spines are often collected together in 

 groups, supported on pedestal-like colunms, which columns 

 with their accompanying spines are called paxillse. Mouth in- 

 ferior, central, sometimes also serving as the vent; a special 

 anal opening is, however, more generally present, on the centre 

 of the aboral surface. Respiration complicated, being partly 

 effected by means of the aboral respiratory tentacles, partly by 

 the ambulacral tentacles, and partly by the entire ciliated epi- 

 thelium of the surface of the body. A madreporiform tubercle 

 — a filter for the admission of water — on the aboral surface of the 

 disk more or less eccentrically placed. Eyes situated at the ex- 

 tremity of the arms. With or without one or two kinds of 

 pincer-like pedicellarise, formed of two opposing calcareous pieces. 

 Sexes distinct. Ovaries ten ; their special openings, when pre- 

 sent (which is not always the case), on the aboral surface, between 

 the origins of the arms. 



Fam. I. Astropectinidae. 

 No special anal opening. Two rows of ambulacral tentacula. 



Genus X. Astropecten, Linck. 



\_Astropecten, Linck, 1733, and Gray, 1841 ; Stellaria, Nardo, 1831 (nom. 

 usit.); Asterias (restricted), Agassiz, 1837.] 



Disk, together with the five long rays, flat above, and covered 

 in every part by closely aggregated paxillse. Two rows of lateral 

 plates, the upper covered with granules, the lower clothed with 

 spines, which are shorter on the inferior portion, and gradually 

 increase in length towards the upper margin, where they are 

 long. Suckers biserial. No anus. Madreporiform tubercle 

 near the margin of the disk. No pedicellarise. Respiratory 

 pores very numerous. 



8* 



