ACTINOPODOUS HOLOTHURIOIDEA. 271 



youngest has a thin, transparent skin, and when fresh had a green 

 tinge. In the two specimens in which the tail is apparent, that 

 portion has a light color. At first glance. Nos. 1G65 and 1666 

 are so different that it appears scarcely possible that they 

 belong to the same species. I hope, however, to show that the 

 striking difference in color is due to the formation, in course of 

 hfe, of the wine-red corpuscles wliich have been stated to be 

 characteristic of so many species. Of tliis, more anon. 



There are 15 tentacles; all are trifid, e. i., there exists a small 

 papilla near, and on each side of, the tip. The calcareous ring is 

 shown in textfig. 55 a. Each of the radiaha has a posterior prolonga- 

 tion ending beliind in two points. Anteriorly it ends also in two 

 points, to which the longitudinal muscles are attached. Interradialia 

 end in a single point anteriorly, without any posterior prolonga- 

 tion. These are all fused together, and there are some longitudinal 

 grooves. Tentacular ampulla) present. Polian vesicle one. Stone- 

 canal with a madreporic knob present. There are minute papillœ 

 around the anus. 



For examination of the calcareous deposits, it is best to cut 

 a longitudinal strip of skin extending from üie base of tentacles 

 to the tip of tail, and to mount it whole or in a definite series, 

 so that one can trace changes in the character of the deposits 

 from one end to the other. Characteristic of the genus are clusters 

 of 4—7 spoon-shaped bodies, scattered here and there. In specimen 

 No. 1129., the spoons measure 0.15—0.17 mm. in breadth at 

 the broad portion and 0.38—0.55 mm. in total length. There are 

 many holes in the entire length of the stem, which ends in short 

 irregular teeth. From the center of each cluster, there arises an 

 anchor which protrudes from the skin and may be felt or seen 

 (c). Each anchor has a slightly enlarged base perforated by some 



