NOTES ON SOME BRITISH NUDIBEANCHS. 373 



seriate, which would seem to be a more primitive arrangement than the 

 extremely narrow raduho of the ^^olids ; but the anal papilla is situated 

 near the end of the back in the median line, which seems to be an 

 instance of secondarily acquired symmetry. The digestive system offers 

 peculiarities of its own ; and the cerata, together with the hepatic 

 diverticula, extend in front of the rhinophores along the anterior margin. 

 There is generally a crest between the rhinophores. 



Three British genera are known — Antiopella, Janolus, and Proctonotus. 

 The nomenclature of tlie first genus is confusing. Verany described it 

 as Janus in 1844, and this name is used by l>ergh, Trinchese, and 

 Vayssiere on the ground that it has priority over Antiojw, the name 

 used by Alder and Hancock in 1855. But the objection to the name Janus 

 (as pointed out by Alder and Hancock in the text fur plate 43) is that 

 it has been in use for a genus of Hymenoptera since 1835. But 

 Mr. Hoyle states (Journnl of Concholoji/, 1902, p. 214) that Antiopa is 

 in its turn invalid for a similar reason, namely, that it was used for a 

 genus of Diptera as early as 1800. He proposes to call the animal 

 Antiopella^ and it would seem that this name must stand, unless some 

 one proves that it also is preoccupied. 



Antiopella has perfoliate rhinophores with a crest between them, and 

 jaws with denticulate edges. Only one species is properly authenticated, 

 A. cristata, which is recorded from the Mediterranean and Britisii 

 waters. Janus sanguineus, Angas, is somewhat doubtful. The plate 

 suggests that it may be an unusually red variety of Madrella ferru(jino.<n , 

 which has also the habit mentioned by Angas of discharging a yellow 

 secretion which colours the water round it. 



The genus Janolus was created by Bergh for a specimen obtained by 

 the Challenger, and differing from Antiopella in having a very broad 

 margin to the foot and remarkably large undenticulate jaws. Bergh has 

 since shown that Alder and Hancock's Antiopa hyalina belongs to this 

 group. A third species, Janolus coeruleopictus, Eliot, is recorded from 

 California; and a fourth, somewhat doubtful, species is described ])elow. 



The genus Proctonotus was created by Alder and Hancock for two 

 specimens found near Dublin, and is also recorded from AVest Ireland 

 and Arran. The rhinophores are not perfoliate (though they bear 

 wrinkles and tubercles), and there is no crest between them. The 

 radula is broad and the jaws are not denticulate. 



ANTIOPELLA CRISTATA (DKLLE CIIIAJE). 



Four living specimens at Plymouth, April, 1905, the largest 30 mm. 

 long and 8 l)road. Alder and Hancock's figure of this species is not very 

 good, and that of Trinchese {yEolididoi del Porto di Genova, pi. 44) is in 



