MONOGBAPH OF THE EXISTING CRINOIDS. 635 



depressed lobe; the sixth are about as long as the second, progressively increasing 

 slightly in length, each slightly concave anteriorly and increasing very suddenly 

 in width near their upper ends, after which the anterior and posterior edges are 

 nearly parallel. The dactyls are very strong and well curved, and each is about 

 two-thirds the length of the corresponding sixth segment. There are no spines 

 on the sixth segment of the last perseopod, as shown in Sars' figure of L. planifrons. 



The uropods are as in L. planifrons, but the telson is less oval and more 

 triangular. 



The perseon and first three segments of the pleon form an evenly curved arch, 

 while the fourth, fifth, and sixth segments of the pleon are sharply deflected 

 anteriorly and lie between the last three perseopods. 



The antennse lie posteriorly against the peraeojjods. 



In this attitude the animal fits snugly into a hole in the disk of the comatulid 

 in which it is about half buried. It probably attaches itself to the disk by means 

 of the strong hook-like dactyls, and the flesh of the crinoid gradually enveloping 

 it forms the cavity. 



The length is 5 mm. 



Locality. — China Sea; Albatross Stations 5310 and 5311. 



Depth.— 88 to 100 fathoms. 



Remarks. — The only other species of this genus, L. planifrons Sars, was re- 

 corded by Sars from three widely separated localities on the coast of Norway. His 

 specimens were all taken in the dredge. He remarks that the semiparasitic char- 

 acter of the species remains an open question. 



It is very interesting to find this second closely allied species parasitic upon 

 comatulids in so distant a locality as the China Sea. 



Type.— C&t. No. 49599, U.S.N.M. 



COPEPODA. 



The great majority of the copepods are free living, but a considerable 

 number of them are truly parasitic, living on the juices of fishes, crustaceans, 

 annelids, and other aquatic animals. Another large group is commensal or 

 semiparasitic, living in the cavities of various marine animals, especially in 

 those of the ascidians, both simple and compound. Others occur on the external 

 surface of sponges, sea urchins, and starfishes. 



In order that the relation between the copepods parasitic on the crinoids 

 and those occurring upon the other echinoderms may be appreciated, I have given 

 a complete list of the latter, wliich follows the discussion of the two species known 

 to be associated with the comatulids. 



Family ASCOMYZONTID^. 



COLLOCIIERES GRACII.ICAUDA (BRADY). 



This species was described in 1880 from Robin Hood Bay, in Yorkshire, in 

 35 fathoms, by Brady under the name of Cyplopicera gracilicauda. In 1888 it 

 was redescribed by Rosoll, who found it parasitic on Antedon adriatica at Trieste, 

 under the name of Ascomyzon comatulw. 



