190 6- 1907.] Copepoda living as Messmates with Ascidians. 365 



D. Normani. The maxillae and foot-jaws, however, are 

 apparently decidedly different in the two species. Canu 

 records D. psyllus from Ascidia virginea and some other 

 Ascidians. 



Van Beneden, in his work on ' Animal Parasites,' divided 

 these creatures into three groups — Messmates, Mutualists, 

 and Parasites ; and the Copepoda mentioned here under the 

 Notodelphyoida he classified with the third, 1 but where he 

 would place the others he does not say. I think, however, 

 that they should all be arranged with the first group, the 

 Messmates, for they do not appear to live on the tissues of 

 their host, but are content to take a share of its food, or to 

 live on the refuse matter in the branchial sac or digestive 

 canal. 



Genus Notopterophorus 0. G. Costa. 



The only species of Notopterophorus I have met with is 

 that which I ascribed to N. papilio Hesse. It is a robust 

 form, and is furnished with dorsal wing- like appendages 

 entirely different from anything met with in other species, 

 while if wanting in these appendages it would scarcely be 

 recognised from a Doropygus. These wings, when perfect, 

 taper off at the corners into long slender filaments, as may be 

 seen in some of the specimens exhibited. N. papilio, though 

 not the only species described, appears to be the one most 

 common and widely distributed. I found it fairly plentiful in 

 large Ascidians dredged in Scapa Plow in Orkney. It has 

 also been obtained in East Loch Tarbert, Loch Fyne, at Oban, 

 and the Shetland and Channel Islands. The appendages, 

 which in some respects resemble the wings of a butterfly, but 

 of course are not used in the same way, can, it is said, be 

 moved with considerable energy, and Dr Brady's remark that 

 the use of these appendages is at present quite unknown, 2 is 

 apparently as applicable now as when it was published. 



I may mention that the species I have here recorded as JSf. 

 papilio Hesse appears to be much more robust than the 

 drawings in the 'Monograph of British Copepoda' (Plate 31) 

 represents that species to be, and therefore it is just possible 



1 'The International Scientific Series,' vol. xx. p. 251 (1876). 



2 'British Copepoda,' vol. i. p. 144 (1879). 



