9O2 



ECHINODEKMA 



beginning to enlarge, to form the centro-dorsal plate (-2, c rf), from 

 which are beginning to spring the dorsal cirrhi (cir) that serve to 



Fm. C>8. Pentacrinoid larva of Aittcdoit. 1. Skeleton of early peiitacrinoid, 

 under black-ground illumination, showing its component plates : l>, It, 

 basuls, articulated below to the highest point of the stem; r l , /', first 

 radials, between two of which is seen the single anal plate, a ; -, second 

 radials ; r"', third radials, giving off the bifurcating arms at their summit ; 

 i>, <>, orals. '2, 3. Back and front views of a more advanced pentacrinoid, 

 as seen by incident light, one of the pair of arms being cut away in tig. ''< 

 in order to bring the mouth and its surrounding parts into view : b, b, 

 luisals; /', /'-', /-"', first, second, and third radials; n, anal, now carried 

 upwards by the projection of the vent, v ; o, u, orals; cii; d<.>r>:il cirrlii, 

 dr\ dojied from the highest joint of the stem. 



