PEAEYNX OF AN UNKNOWN HOLOTIIUKIAN. 2G1 



in so far as they are represented by the loose spicules which 

 Charles Stewart first showed to be present in the walls of the 

 pharynx of the Echinidse. 



EXPLANATION OF PLATE XXIII. 



Illustrating Mr. H.N. Moseley's Memoir on "The Pharynx 

 of an unknown Holothurian of the Family Dendrochirotse/^ 

 in which the calcareous skeleton is remarkably developed. 



Fig. 1. — View of the outside of tlie pharynx of a Holothuriau of the Family 

 Dendrochirotae opened by an incision along the dorsal middle line, and spread 

 out so that the ventral middle line lies in the centre of the figure. The water 

 vascular ring and digestive tract are torn away from the hinder extremity. 

 Enlarged five diameters. R. Radial annulare or component plate of the 

 calcareous ring. I. Interradial annulare. IF. Radial annulare of the ventral 

 middle line smaller than the others, not perforated or forked anteriorly. 

 V. One of the two ventral interradial aunularia different in form to the 

 others. B. One of the radial series of pharyngealia, or plates covering the 

 pharynx behind the annulus. C. Hinder prolongation of another such series 

 enclosing a tentacular canal, and ending in a torn extremity where the water 

 vascular ring was situated. A. One of the lateral interradial pharyngealia, 

 with minute intercalated ossicles. T. Slight tentacular pouch, formed by the 

 anterior prolongation of the pharynx. 



Fig. 2. — One of the two small ventral tentacles enlarged. 



Fig. 3. — Spicules from the tentacles. 



VOL. XXIV. NEW SER. 



