226 Proceedings of the Royal Physical Society, 



very small, but it must be further reduced, because of the 

 impossibility of determining with certainty the species re- 

 ferred to by many of the older writers, on account of the 

 confusion which has existed between some of the allied forms, 

 and the tangled mass of synonymy in which other species 

 have become hopelessly involved. Accordingly, with the 

 exception of Alder's two species of Parascklia from the Isle 

 of May, and of Pelonaia corrugata (F. and G.), which was 

 first discovered by Professor Goodsir, in deep water, off 

 Anstruther, in 1841, and which was dredged near the Bass 

 Rock in 24 fathoms by the German North Sea Expedition of 

 1872, we have given in the following list only those species 

 wliich we have ourselves collected in the Firth of Forth. 



ASCIDIyE SIMPLICES. 



MOLGULID^. 



Molgula citrina (Alder and Hancock). 



This little species was first described by 

 Alder in his " Catalogue of the ]\Iarine 

 MoUusca of Northumberland and Dur- 

 ham," * and, so far as we are aware, it has 

 not been mentioned since. 

 We have come upon it several times dur- 

 ing the last two years, adhering to the 

 under surfaces of large stones, about low 

 water mark, between the Chain Pier and 

 Granton Harbour. 



Eugym ghUinans (Moller). 



This species has a most extensive syno- 

 nymy, and is usually known as Molgula 

 (or Eugyra) arenosa (Aid. and Han.). 

 Lately, however, Traustedt -|- has declared 

 that it is identical with the species de- 

 scribed in 1842 by Moller + as Cynthia 

 glntinans. 



* Trans. Tyneside Nat. Field Club, vol. i., p. 199 (1850). 

 + Oversigt o. d. f. Danmark, etc., Asc. Simix (Yid. Medd. nat. For. 

 Kblivn, 1879-80). 

 X Index. Moll. Groenl., 1842, p. 21. 



