454 THE OPISTHOBRANCHIATE 



33. IdaliellAj Bergh} 



48. *Idaijella (Idalia) aspersa, A. and H. 



Only tlie two specimens described in my previous Report have 

 been obtained by us. 



34. AnculAj Loven. 



49. "^Ancula ceistata, Alder. 



Only four additional specimens liave been obtained. Three were 

 found on the north side of Drake's Island at low water, one about the 

 middle of May and two on the 3rd of June. These individuals 

 were mature, but a small one -^ inch long was taken with the 

 bottom tow-net in Cawsand Bay on the 7th July. It bore a speci- 

 men of the remarkable parasitic Copepod, 8planchnotrophus, whose 

 egg- sacs protruded through the back of the animal just in front of 

 the anus. Two days later the parasite with its long tentacle-like 

 processes had crawled out of the Ancula, which was only half its 

 original size, and was being steadily devoured. 



Professor Herdman^ has found this species in extraordinary 

 profusion at Hilbre Island during the breeding season ; on one reef 

 of rocks " for yards it was impossible to walk without treading on 

 them, and handfuls were readily collected by scraping the specimens 

 together from the mud-covered rocks." He also finds that the 

 animal loses much of its conspicuous yellow coloration with age, and 

 records some interesting observations on its means of defence against 

 waves and strong currents (cf. A. R. Hunt, Journ. Linn. Soc, xviii, 

 p. 265). 



Polycerinse. 



35. Thecacera, Fleming. 



50. *Thecacera pennigera, Montagu. 



We have not yet obtained another specimen of this species. 

 Mr. Vallentin dredged a single specimen in Falmouth Harbour dming 

 the spring among oyster- valves covered with Bugula flabellata. 



' Bergli, Veher (lie Qattung Idalia, Arch fiir Naturgesch., xlvii, i^ p. 7. See also 

 Norman on the name Idalia, loe. cit., p. 74-, 



'^ Herdm;m and Clubb, Third Report, p. 134; cf. also the Second Report, p. 227, and 

 First Report, 1886, p. 270, and Thompson, Ann. Mag. Nat. Hist., 1800, p. 51. 



