362 Copepoda living as Messmates with Ascidians. [Sess. 



species as well. Notodelphys Allmani, besides being the most 

 common, appears to be also the largest, of the various species. 

 According to M. Thorell, they sometimes measure five 

 millimetres in length, but the largest Scottish specimens I 

 have noticed scarcely reach four millimetres. This form 

 has long tail-segments, and the dorsal egg-pouch in the case 

 of adult females is usually coloured and distended with 

 ova, so that the specimens are conspicuous enough. 



Notodclphys prasina is also of frequent occurrence, but it is 

 not so common as the one just referred to. Though resem- 

 bling that species in some respects, it is smaller, and is, besides, 

 readily distinguished from it by the very short tail-segments. 

 Rev. A. M. Norman, who collected this species at Oban, found 

 it to be more abundant there than any other of the Entomo- 

 straca taken from the branchial sacs of Ascidia mentula. He 

 has also recorded it as occurring in the same Ascidian in 

 Shetland. 1 I have taken a number of specimens in large 

 Ascidians dredged in East Loch Tarbert, Tarbert Bank, and 

 Kilbrennan Sound, Eirth of Clyde. 



Notodelphys agilis is apparently less common than the 

 others. Like N. Allmani, the tail - segments are elongated, 

 and its appearance being otherwise somewhat similar to that 

 species, the one might be easily mistaken for the other were 

 it not that N. agilis is a distinctly smaller form. Dr Brady 

 reports its occurrence off the coasts of Durham and Yorkshire, 

 and at Shetland on the authority of Rev. A. M. Norman. I 

 have obtained it very sparingly in the Firths of Forth and 

 Clyde. 



Notodclphys coerulca. — Dr G. S. Brady states that this 

 species differs scarcely at all from Notodelphys Allmani, and 

 that he cannot find any good reason for separating it from 

 that species. 2 He records it as having been obtained in 

 Corella (Ascidia) parallelogramma and Ascidia vcnosa. I 

 have not been able to identify this form among any of the 

 Notodelphyidae examined by me. 



Other species of Notodelphys have been described as Noto- 

 delphys clegans Thorell, rufcscens Thorell, and tenera Thorell, 



1 'British Copepoda,' by Dr G. S. Brady, vol. i. p. 132 (1879). 



2 Ibid., p. 130. 



