128 



ECHINODERMS OF THE BRITISH ISLES 



Brisinga. There are no papulae on disk or arms. No unpaired, 

 shield-shaj)ed interradial plate on the oral side, separating the 

 first adanibulacrals. Rays 6-13, very exceptionally {Fr. sex- 

 radiafa) only 5. The articulation between first and second 

 adambulacral plates or between the upper end of second and 

 third ambulacral plates not ligamentous, syzygial. One pair of 

 genital organs to each ray. 



Fig. 74. — Freyella Edwardsi. (After Koehler, Monaco, Fasc. xxxiv.) 



Possibly some of the east Atlantic species really belong to 

 the genus Freyellaster Fisher, which is distinguished from Freyella 

 in having a ligamentous (syzygial) articulation between the first 

 and second adanibulacrals and between the upper end of second 

 and third ambulacrals, and by having numerous genital organs 

 in each ray. The species spinosa and sexradiata, however, are 

 known with certainty to belong to the genus Freyella (Fig. 74). 

 Key to the East Atlantic species of the genus Freyella. 



1. Arms 11-13 2 



Arms 6 (5)-8 3 



2. A conspicuous naked dorsal interradial plate at the base of each pair 



of arms. No furrow spine ; outer adambulacral spine in proximal 

 part of arm widened at the point. Fr. Edwardsi E. Perrier 



