MONOGRAPH OF THE EXISTING CKINOID3. 637 



OSTKACODA. 



On a specimen of Metacrinus zonatus dredged by the Albatross at Station 

 5186, in the Tawi Tawi group, Philippine Archipelago, in 80 fathoms, I found 

 a peculiar parasitic ostracod firmly attached to the column. 



CIRRIPKDIA. 



From their mode of life as attached organisms and their fixation to every 

 possible kind of support (they have even been found on the tail feathers of 

 Priofinus cinereus) it is quite to be expected that the barnacles should be found 

 living upon the crinoids ; indeed, it is rather surprising that this is not more often 

 the case. 



The columns, and especially the cirri, of the pentacrinites frequently support 

 stalked barnacles, and they sometimes occur on the cirri of the larger comatulids 

 of the deeper waters, mostly those of the family Thalassometridse. There is a 

 record of one attached to a pentacrinite arm. Sessile barnacles have been found 

 only on the pentacrinites and usually occur on the stem, though sometimes on 

 the cirri. 



But barnacles are not nearly so abundant, either in number of species or in 

 number of individuals, upon the crinoids as they are upon the urchins, especially 

 upon the dead spines of the cidarids. 



There is no evidence that the barnacles attached to the crinoids find in the 

 latter anything more than a convenient object for attachment, such as they would 

 find equally well in a long urchin spine. 



Nearly all of the barnacles are inhabitants of relatively shallow water, and 

 Scalpellum is the only genus which is often met with in the deeper portions of 

 the sea, into which it descends to a depth of 2,850 fathoms. This sufficiently 

 explains the fact that most of the barnacles which have been found upon the 

 crinoids belong to this genus. 



The pentacrinites of the intermediate depths are the recent crinoids most 

 extensively represented as fossils in the secondary rocks, and the same is true 

 of Scalpellum among the recent barnacles. 



None of the Acrothoracica or Apoda have as yet been found in association with 

 the crinoids. 



The Rhizocephala are apparently all parasites of malacostracan, and chiefly 

 of decapod, crustaceans, though von Willemoes-Suhm in his notes written on board 

 the Challenger mentions a species which he found in the pouch of a starfish of 

 the genus Hymenaster, where it was possibly introduced by accident, and a 

 Bopyrus or Peltogaster from an ophiuran. 



The Ascothoracica are known as parasites in corals, antipatharians, and star- 

 fishes (Henricia, Hippasteria, and Solaster) but are not known to occur in the 

 crinoids. 



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