REPORT ON THE ECHINOIDEA — MORTENSEN 253 



imen here described. To which species they belong can not be 

 determined at present; but it must also be kept in mind that the 

 reference of the present small specimens to H. elegans is not beyond 

 doubt either. H. L. Clark 3 points out that the pedicellariae of the 

 Siboga specimens are peculiar; however, I find the pedicellariae in the 

 young specimens from the Albatross collection very much like that 

 figured by de Meijere, and also in larger specimens of undoubted H. 

 elegans one may find small tridentate pedicellariae which are quite 

 similar. 



Genital pores are not yet developed in specimens of 14-16 mm. in 

 horizontal diameter; but by the time they have reached a size of 24 

 mm. in horizontal diameter the pores have made appearance. The 

 interradial plates of the peristome as a rule do not begin to 

 appear until somewhat later, at a size of about 27 mm. horizontal 

 diameter. In a specimen of 14 mm. horizontal diameter I find, how- 

 ever, one interradial plate on the 

 peristome in one of the interradii, the 

 others remaining naked. 



One of the specimens from station 

 5656 is especially interesting. It is 

 the largest of all, measuring 50 mm. 

 in horizontal diameter, and is unus- 

 ually high, 44 mm., being in fact 

 quite egg shaped. (PI. 52, fig. 1.) 

 There are nine coronal plates. On 

 several of the proximal ones the pri- 

 mary spine has been lost, and in its 

 place a varying number of second- fig. 7— apical system of young histoci 

 aries have developed. The speci- DARIS ELEGANS ' 0F 7 MM - DI * METER - xu 

 men is a naked test, broken and in a poor state of preservation, but this 

 is evidently not merely due to its having been roughly handled at the 

 capture. Some of the areoles are perforated, which very probably 

 means that the specimen was about to be devoured by some large gas- 

 tropods at the moment when it came into the trawl. Nearly all the spines 

 are lost, and most of the areoles are perfectly clean, which certainly can 

 not be due to the rough treatment in the trawl. Apparently the speci- 

 men was already dead and had lost nearly all its spines when it was 

 captured by the trawl. But it could only quite recently have died, 

 as the intestine is still partly preserved and the peristomial membrane 

 is still intact. Whether the specimen was killed by the mollusks or 

 they only began to devour it after it was dead can not definitely be 

 said, but the fact that most of the spines were already entirely lost, 

 their muscles having completely disappeared, would rather indicate 

 that the specimen had died of old age and then was about to be eaten 

 by the gastropods. 



3 Bull. Mus. Comp. Zool., vol. 51, 1907, p. 227. 



