DEVELOPMENT OF ANTEDON (COMATULA, LAMK.) EOSACEUS. 



749 



Fig. 5. Dorsal Cirrhi in various stages of growth aiid development : — «, typical mature 

 cirrhus ; b, c, d, e, f, successive stages of incomplete type ; g, h, i, k, I, suc- 

 cessive stages of complete type ; m, n, cirrhi presenting most of the characters 

 of maturity, but having less than the normal number of segments, and deficient 



in the opposing process.- 



-Magnified 45 diameters. 



Fig. 



PLATE XXXIII. 



Fig. 1. Pentagonal Base of the Calyx of Antedon rosacens, formed by tlie coalescence of 

 the five First Radials, its dorsal surface (shown in fig. 2) having been removed, 

 so as to lay open the radiating Axial Canals, o, a, and their communicating 

 branches, b, b ; around the central space is an irregular calcareous network, 

 formed by the inosculation of processes sent off from the internal faces of the 

 First Radials. — Magnified 25 diameters. 



Fig. 2. Pentagonal Base of the Calyx, formed by the coalescence of tlie five First Eadials, 

 with the Rosette in situ, as seen from its dorsal aspect, the Centro-dorsal plate 

 having been removed. — Magnified 25 diameters. 

 Pentagonal Base of the Calyx, formed by the coalescence of the First Radials, 

 as seen from its ventral aspect : — the central aperture for the passage of a 

 prolongation of the Crinoidal Axis is surrounded by irregular processes from 

 the inner margins of the First Radials, which connect themselves with the 

 central portion of the Rosette ; the oblique sides of the pentagon form the 

 surfaces of articulation for the Second Radials. — Magnified 25 diameters. 

 Centro-dorsal plate, seen from its dorsal side after the removal of the cirrhi ; 

 showing its flattened central portion surrounded by between two and three 

 circlets of articular sockets.— ^lagnified 15 diameters. 

 Lateral view of the same, showing the alternating arrangement of the sockets. 

 — Magnified 15 diameters. 



Fig. 6. Centro-dorsal plate, seen from its ventral side after its detachment from the 

 Pentagonal Base, showing its basin-hke cavity, the bottom of which is per- 

 forated by minute apertures for the passage of the axial cords of the cirrhi ; 

 on the inturned lip of the basin are five shallow depressions, a, a, corresponding 

 to the spout-like processes of the Rosette. — Magnified 15 diameters. 



Fig. 7. Portions of Base of Calyx at origin of Rays, in the variety showing Interradial 

 Plates :— c, Centro-dorsal ; r', r\ Second Radials ; r', r\ Third Radials : at A 

 these interradials are numerous, minute, and dissociated, and are obviously 

 perisomatic in their character ; at b they are fewer, larger, and more com- 

 pactly arranged. — Magnified 30 diameters. 



Fig. 8, Segments of Dorsal Cirrhi ; a, basal, b, from middle of length ; showing the 

 central passage surroimded by a prominent annulus, with depressions on either 

 side for the attachment of ligaments. — Magnified 70 diameters. 



Fig. 4 



Fiff. 5. 



