134 Dr. R. Bergh on Phidiana lynceus. 
Margo masticatorius mandibule minutissime longitudinaliter ph- 
catus. Dentes radule uniseriati. Dentes pectiniformes, medio emar- 
ginati. 
Only four species can with certainty be classed under Phi- 
diana, viz. Ph. inca (d’Orb.), Ph. patagonica, VOrb., Ph. wni- 
lineata, A. & H., Ph. lynceus, Bgh., n. sp. Perhaps 4. Al- 
deriana, Desh. (Frédol?, ‘Le Monde de la Mer,’ 1864, p. x1, f.7) 
and 4. northumbrica, Ald. & Hance., also belong to Phidiana. 
An anatomical examination of Ph. lynceus, Bgh., affords several 
interesting results, particularly with regard to the organs of 
vision. ‘The eye was observed in the middle of the external 
margin of the cerebro-visceral ganglion. Immediately behind 
the eye, and a little further in, another, smaller, shortly pedun- 
culate globular body was observed, which proved to be an 
accessory eye; the diameter was 0°05 to 0°06 millim., the 
pigment black, the lens small, colourless, with a small yellowish 
kind of nucleus. Close behind the accessory eye a vesicle, spa- 
ringly filled with cells and nuclei, with thin walls, was seen to 
protrude from the surface of the ganglion. This vesicle might 
be the auricular vesicle ; no other organ that could be so in- 
terpreted was found. Whilst plurality is a frequent phenome- 
non amongst Acephala and Tunicata, no instance of the normal 
occurrence of more than one pair of eyes was hitherto recorded 
in the class of Gasteropoda. The earlier statements concern- 
ing the occurrence of such an arrangement in the genus Diplom- 
matina (Bens.) turned out to be founded on a misconception *. 
Nor was Claparéde able to find the black spot which Moquin- 
Tandon stated he saw in Neritina fluviatilis behind the true 
eye, and which he described as being like an accessory eyeT. 
Agassiz states, in his ‘ Lectures on Comparative Embryology,’ 
1849, p. 86, that on a little Margarita from the roadstead: of 
Boston, he had seen a row of eyes placed at the base of the 
tentacles of the epipodial frmge. But this statement is not 
borne out by the results of a careful examination of M. grén- 
landica and M. cinerea. When viewed from beneath, the ten- 
tacles of the epipodial fringe in M. grénlandica, Ch., are seen 
to issue each from a small depression, of which the inner mar- 
gin is almost always swollen in the middle, and contains a 
varying quantity of black pigment; sometimes this pigment 
is disposed in the shape of a ring, and in that case these tu- 
bercles assume a striking similarity to eyes. These tubercles 
resembling eyes are of very different shapes, sometimes rather 
oval; in some cases the pigment is continued along the lateral 
* Comp. A. Adams in ‘Ann. & Mag. N. Hist.’ ser. 2. vi. 1860, p. 118, 
and zbid. xii. 1863, pl. vii. figs. 11, 12. 
+ Comp. Claparéde in Miiller’s ‘Archiv,’ 1857, p. 1389, and Moquin- 
Tandon in ‘ Hist. Nat. des mollusq. fluy. et terr. de la France,’ il. p. 22. 
