1904-1905-] Copepoda living as Parasites or Messmates. 205 



Leiochone " is a very rare worm on our English coast, and 

 seems to have been unrecorded " previous to his discovery of 

 it at Hunstanton ; and he suggests that a search might be 

 made for the worm and its parasite where any remains similar 

 to those referred to were known to exist. It would no doubt 

 be interesting if it could be satisfactorily shown that there 

 was any real connection between the remains of submarine 

 forests and this particular worm and its copepod lodger. 



5. Some Copepoda found on othei' species of Crustacea. — The 

 claim which these copepods make on their larger and well-to- 

 do relatives for shelter and food is more in harmony with the 

 nature of things than are some of the examples already 

 mentioned ; and, curiously enough, genuine parasitic habits are 

 more frequently observed among the Copepoda living with other 

 crustaceans. A peculiar group that forms the subject of a 

 most interesting monograph by Dr H. T. Hansen, of Copen- 

 hagen, are all true parasites. In this monograph nearly fifty 

 species have been described and figured, and the number is 

 still being added to. They have been found on various 

 crustaceans, including those belonging to the Carida, the 

 Schizopoda, the Cumacea, and the Isopoda. But it is on the 

 Amphipoda that the largest number have been observed. Of 

 the species already described, over thirty have been found on 

 amphipods, and it is in the marsupium of these crustaceans 

 that they are usually met with. The following species occur 

 in the Forth estuary : Aspidoecia Normani infests the Schizo^ 

 pods, Erythrops elcgans and Erytlirops erythrophthalmus (some- 

 times recorded as Erythrops Goesi). Sphoironella minuta variety, 

 found in the marsupium of the Amphipod Megamphopus 

 cornutus ; and the closely allied Salenskya tuherosa, which 

 occurs in the marsupium of another Amphipod, Ampelisca 

 spinipes. These parasites are for the most part very small, of 

 a globular form, and rather difficult to diagnose satisfactorily. 

 But the species to which I am now to refer is a considerably 

 larger one, and belongs to a more highly -developed group. 

 Its name is Sunaristis paguri, because it is found in the same 

 shell with, and is supposed to be a commensal of, the common 

 hermit crab (Eupag^iriis Bernhardus). I have found it in the 

 Cromarty Firth, and my son has taken it in the estuary of the 

 Mersey. When searching for specimens, the method adopted 



