NOTES ON SOME BrxITISH NUDIBRANCHS. 367 



AMPHORINA AURANTIACA (A. & H.). 



(Alder and Hancock, Mon. Brit. Nvd., Fam. 3, i)I. 27. 

 Beaumont, I.e., pp. 836-7.) 



One living specimen examined at Plymouth, April, 1905. The 

 animal, which was active and seemed to resent being touched, 

 measured 8 mm. in length and 3"5 in breadth when extended. 

 Mr. Beaumont observes that specimens as highly coloured as Alder and 

 Hancock's plate are rare, and the present one was decidedly less 

 brilliant. The tentacles and rhinophores were colourless, the latter 

 with a faint red tinge. The body was colourless and transparent, with 

 very minute, hardly visible opaque white dots. Behind the black eyes 

 was a reddish spot, possibly caused by some internal organ showing 

 through the skin. The general effect of the cerata was that they were 

 reddish with white tips. The integuments of the cerata were colour- 

 less, as could be seen at the tips, where there is no liver ; below this 

 colourless tip was a broad band of opaque white, formed by an aggrega- 

 tion of minute dots. The hepatic diverticula were reddish brown. 



The foot is expanded anteriorly into a disk, but there are no tenta- 

 cular angles. The tail does not project beyond the cerata behind. Tlie 

 rhinophores are somewhat longer than the tentacles. In the living 

 animal the cerata show no distinct arrangement in rows ; a bare space 

 is visible anteriorly behind the rhinophores ; further back the cerata 

 close over and hide the dorsal surface. When stripped off, the cerata 

 are seen to be arranged in ten rows, each containing two to four. 



The jaws bear several series of minute denticles. The radula con- 

 sists of a single series of seventy-six teeth, tapering markedly in 

 breadth. They bear two or three main denticles (Fig. 17.) on each side 

 of the median cusp, and one or two secondary smaller denticles occa- 

 sionally and irregularly interposed between the main denticles. All the 

 denticles, especially the median cusp, arise unusually far back. Mr. 

 Beaumont states that the penis is armed with a style. 



Verril in Proc. U. S. National Mus., iii., 1880, p. 390, observes that 

 Cuthona aurantiaca, A. & H., is very closely allied to Gratcna gymnota 

 (Gould), whicli lias been described by Bergh in Bcitrdge zur Kcnntniss 

 der ^olidiaden, viii., 1885, pj). 33-5. The dentition agrees exactly, but 

 the form and arrangement of the cerata are different, and Bergh found 

 no armature on the penis. It may therefore perliaps be well to keep 

 the forms provisionally distinct. 



This form must, I think, be referred to Amjj/iorhia, for it has all the 

 main characters of that genus. The cerata are stout (see Alder and 

 Hancock), the penis is armed with a style (according to Beaumont), the 

 radula is tapering, and the denticles on the teeth arise far back. Loman 



