DF\^ELOPMEXT OF ANTEDOX (COMATULA, LAMK.) EOSACEUS. 755 



Fig. 5. Skeleton of the Calyx of a Pentacrinoid nearly ripe for detachment, as seen from 



its internal or ventral aspect, the centro-dorsal plate having been removed ; 



b, b, Basals ; r\ r\ First Radials. — Magnified 50 diameters. 

 Fig. 6. The same, as seen from its external or dorsal aspect : — c, central pore for the 



passage of the sarcodic axis through the Centro-dorsal plate ; b, b, Basals ; 



r\ r\ First Radials ; r', r^ Second Radials ; J*', r\ Third or Axillary Radials ; 



br\ br\ Brachials ; a, Anal. — Magnified 50 diameters. 



PLATE XLII. 



Fig. 1. Incipient Rosette (see Plate XXXIII. figs. 10, 11) formed by the coalescence 

 of the five altered Basals, in a young Antedon. — Magnified 120 diameters. 



Fig. 2. Skeleton of Base of Calyx of young Antedon, seen from its internal or ventral 

 side ; showing the five basals {h) altered by endogenous growth, in preparation 

 for the formation of the Rosette. — Magnified 100 diameters. 



Fig. 3. Calyx of young Antedon just detached, seen from its dorsal side, showing five 

 Cirrhi of the mature type and five of the rudimentary type, the Radial and 

 Brachial plates, and the extension of the visceral disk as far as the Third 

 Radial. — Magnified 25 diameters. 



Fig. 4. Skeleton of the terminal portion of the Arms of a mature Pentacrinoid :— A, ven- 

 tral aspect ; b, dorsal aspect. — Magnified 100 diameters. 



Fig. 5. Skeleton of the basal portions of the Arms of a mature Pentacrinoid : — a, ventral 

 aspect ; B, dorsal aspect. — Magnified 100 diameters. 



Fig. 6. Skeleton of base of Calyx of young Antedon, seen from its ventral aspect; 

 showing the five Basals grouped around b, and traversed by canals for the 

 radiating cords of the sarcodic axis, of which a trunk enters each basal from 

 the central space, and then subdivides into two branches, that pass into the 

 two Radials between which the salient angle of the basal projects ; thus each 

 First Radial receives cords from two basals, and these are lodged in two Canals 

 which coalesce into one towards its distal border, each of them having first 

 become connected by a lateral branch with the like canal in its contiguous 

 First Radial. — Magnified 70 diameters. 



Fig. 7. The same viewed from its dorsal aspect, the Centro-dorsal plate having been 

 removed ; showing that the central space around b on the under side has been 

 enlai'ged by the absorption of part of the original Basals, though it is still con- 

 tracted, nearer the cavity of the Calyx, by the secondary endogenous growth : 

 the system of Axial Canals is displayed as in the preceding figure. — Magnified 

 70 diameters. 



