64 SPOLIA ZEYLANICA. 



can be made out. The specimen is dark brown on the bivium 

 and a lighter shade on the trivium. 



Internal Structure. — Koehler & Vaney state that the 

 calcareous ring is similar to that of Holothuria glaberrima. 

 So far as the shape is concerned this is true, but the calcareous 

 ring of Holothuria lubrica is much larger and more massive 

 than that of the other species. There is a single Polian 

 vesicle 12 mm. long and numerous stone canals, about eight 

 on each side of the dorsal mesentery, having a mean length of 

 about 5 mm. The specimen under examination has ejected 

 its viscera, so that I cannot say whether Cuvierian organs are 

 present or not. Ludwig is the only writer who records the 

 presence of Cuvierian organs. 



Spicules. — These consist of spinous rods varying in length 

 from 112 \i to 148 jx, and having a mean length of 127 ^. 

 The rods are often curved, and have fine spines along their 

 length. The extremities are spinous and often perforated. 



General Distribution. — Indo -Pacific region. 



My examination of Holothuria glaberrima and the above 

 species shows differences of three kinds : — (1) The large size of 

 the calcareous ring of lubrica and the small size of that of 

 glaberrima ; (2) the presence of numerous small stone canals 

 on both sides of the dorsal mesentery in H. lubrica. and the 

 presence of only one extremely large stone canal in H. 

 'glaberrima ; (3) the nature of the spicules as described above. 



Whether the first of these differences is constant, I cannot 

 say. Selenka, however, states that the calcareous ring of 

 H. glaberrima is large, whereas I find it very small. Koehler 

 & Vaney also speak of the calcareous rings of the two species 

 as being identical. In my specimens they are similar in 

 shape but not in size. 



The difference in the number and size of the stone canals 

 may not apj)ear to be a very important one, since it is well 

 known that these organs are very variable ; but it is doubtful 

 whether the variability is so great as shown by the sj)ecimens 

 I have examined. Most of the records of the two species 

 lend support to my emphasis of this difference. Nevertheless 

 Ludwig (31) describes a specimen which had spicules like 



