4-2 



or. in. = Oral tentacle. 



ov. = Ova. 



ovr. — Ovary. 



pd. = Pedal plate. 



•pmb. 1. = First primibrachial. 



pmh. 2. = Second primibrachial. 



pn. = Pinnule. 



pnt. com. = Pentagonal com- 

 missure. 



pr. ten. — Primary tentacles. 



r. cce. — Right ccelom. 



tad. nv. = Radial cords of apical 

 nervous system. 



rd. — Radial plate. 



ros. — Rosette plate. 



rii. hi/. = Rudiment of hydroccel. 



r. w. V. = Radial water vessel. 



sac. — Sacculus. 



sb. c. nv. /. = Sub-epithehal nerve 

 fibres. 



sec. 1. = First secundibrachial. 

 s. te. ca. = Sub -tentacular canal. 

 se. ten. = Secondary tentacle. 

 sn. pp. ^ Sensory papilla. 

 5. n. s. = Sub-neiural sinus. 

 sph. jb. = Fibres of sphincter 



muscle in transverse section. 

 sp. or. = Spongy organ. 

 st. = Stomach of larva. 

 syz. -^ Syzygy. 

 ten. — Tentacle. 

 ^e.s. = Testis. 

 t(j. cl. = Tegmen calycis. 

 tn. vs. = Tentacular vessel. 

 tr. com. = Transverse commissure 



of radial cords. 

 V. f. = Valvidar fold. 

 vn. nv. = Ventral nerves from 



brachial cord. 

 w. t. = Water tube. 



Plate I. 



Fig. 1. Antedon hifida, vsKowiug the attitude assumed by 

 the animal wheu at rest. Natural size. 



Fig. 2. Antedon hifida, shoAviug the disposition of the 

 arms in swimming. Natural size. 



Fig. 3. Antedon hifida, viewed from the aboral surface. 

 The cirri were removed from two-thirds of the 

 periphery of the centro-dorsal to show the 

 bases of the arms. x 5. 



Fig. 4. A radial plate, viewed from the axial face, x 8. 



Fig. 5. Abaxial (outer) face of a radial plate. x 8. 



Fig. 6. Lateral face of a radial plate, x 8. 



Fig. 7. Oral face of a radial plate, x 8. 



Fig. 8. Axial face of a hrst primibrachial. x 8. 



