1891.] Mr Cooke, On Parasitic Mollusca, 2~\ 7" 



Borneo, as ' living in the body of a starfish.' In the British 

 Museum there is a specimen of Pileopsis crystallina in situ on 

 the ray of a starfish. On the brittle starfishes {Ophiuridae) occur 

 several species of Stiliferina. (c) Echinoidea. Various species of 

 Stilifer occur on the ventral spines of echinoderms, and are some- 

 times found imbedded in the spines themselves. St. Turtoni 

 occurs on the British coasts on several species of Echini, and 

 Montacuta substriata frequents Spatangus purpureus and certain 

 species of Amphidetus, Cidaris and Brissus. Lepton parasiticum 

 has been described from Kerguelen I. on a Hemiaster, and a new 

 genus, Robillardia, has recently been established 1 for a Hyalinia- 

 shaped shell, parasitic on an Echinus from Mauritius, (d) Holo- 

 thuroidea. The 'sea-cucumbers' afford lodgement to a variety 

 of curious forms, some of which have experienced such modi- 

 fications that their generic position is by no means established. 

 Entoconcha occurs fixed by its buccal end to the blood-vessels of 

 certain Synaptae in the Mediterranean and the Philippines. Ento- 

 colax has been dredged from 180 fath. in Behring's Straits, attached 

 by its head to certain anterior muscles of a Myriotrochus 2 . A 

 curious case of parasitism is described by Voeltzkow 3 as occurring 

 on a Synapta found between tide-marks on the I. of Zanzibar. 

 In the oesophagus of the Synapta was found a small bivalve 

 (Entovalva), the animal of which was very large for its shell, and 

 almost entirely enveloped the valves by the mantle. As many as 

 five specimens occurred on a single Synapta. In the gut of the 

 same holothurian lived a small univalve, not creeping freely, but 

 fixed to a portion of the stomach wall by a very long proboscis 

 which pierced through it into the body cavity. This proboscis 

 was nearly three times as long as the animal, and the forward 

 portion of it was set with sharp thorns, no doubt to make it to 

 retain its hold and resist evacuation. Various species of Eulima 

 have been noticed in every part of the world, from Norway to 

 the Philippines, both inside and outside Holothurians 4 . Stilifer 

 also occurs on this section of echinoderms 5 . 



On Annelida. Cocliliolepas parasiticus has been noticed under 

 the scales of A coetes lupina (a kind of ' sea-mouse') in Charleston 

 Harbour 6 . 



On Crustacea. A mussel, § in. long, has been found 7 living 

 under the carapace of the common shore-crab (Carcinus maenas), 

 but this is not so much a case of parasitism as of involuntary 



1 E. A. Smith, Ann. Mag. Nat. Hist. 1889 (i), 270. 



2 Journ. de Conch. (3) xxrx. 101. 



3 Zool. Jahrb. Abth. f. Syst. v. 619. 



4 See especially Semper, Animal Life, Ed. 1, p. 351. 



5 Gould, Moll, of U.S. expl. exped. 1852, p. 207 (St. acicula, from Fiji). 

 « Stimpson, Proc. Bost. Soc. iV. H. vi., 1858, p. 308. 



7 Pidgeon, Nature, xxxix. p. 127. 



