Dr. Johnston on Scottish Mollusca. 125 



low and red ; back with some scattered branchial papillae. 

 Plate II. fig. 14—16. 



Doris quadrilineata?? Mull. Zool. Dan. tab 17. jig. 4—6. 

 Hob. On oyster shells from Prestonpans Bay. 



Desc. Body limaciform, three lines long, convex dorsally, 

 truncate in front, tapered and somewhat keeled posteriorly, 

 variegated with black, yellow and red disposed in lines and 

 circular patches in an areolar fashion. Mouth inferior. Ten- 

 tacula two, dorsal, short and ovate, imbricate, contractile. 

 Eyes none. Cloak closely fitted to the body without any ex- 

 pansions, but raised into a narrow crenulate fold along each 

 side, with three pale papillae on it about half-way between the 

 head and tail, and a few smaller papillae on the medial line 

 above the tail. Branchiae in the form of two ovate papillae 

 smaller than the tentacula, placed about the middle of the 

 back, of a dark colour with yellow apices. Foot flesh-coloured, 

 oblong. 



This beautiful animal has a more coriaceous skin than any 

 of its order, and is remarkable for the darkness as well as for 

 the disposition of its colours. Its motions are slow, and I rarely 

 saw it swimming in a reversed position as most of the Nudi- 

 branchiae are fond of doing. A considerable number of cal- 

 careous spicula enter into the composition of the cloak or skin : 

 they are simple, slightly curved, cylindrical, rounded at each 

 end. The red patches of colour depend on the viscera, and 

 may be expected to vary according to the nature of the food 

 and the animaFs state of repletion. 



EXPLANATION OF THE PLATES. 



Plate II. Fig. 1. Doris tuberculaia, the figure taken from a small speci- 

 men. — Fig. 2. The same seen from below, with the penis protruded. — 

 Fig. 3. The dorsal tentacula as seen through a common magnifier. — Fig. 4, 

 5, 6. Doris obvelata in various positions. — Fig. 7. A branchial leaflet as 

 seen through a magnifier. — Fig. 8. Doris bilamellata, in three positions, 

 of the natural size. — Fig. 9. Doris pilosa, natural size. — Fig. 10. The 

 branchial leaflets as seen through a magnifier. — Fig. 11, 12, 13. Doris 

 Barvicensis, in three positions. — Fig. 14, 15, 16. Triopa nothus, in three 

 positions, the figures all greatly enlarged. — (Fig. 15. is reversed on the 

 Plate, as is also fig. 12.) 



Plate III. Fig. 1. Tritonia Hombergii of the natural size. — Fig. 2. The 

 same seen from below, from a smaller specimen. — Fig. 3, 4. Tritonia pi e- 

 beia of the natural size. — Fig. 5, 6, 7, 8. Melibea coro?iata, in different 

 positions: the three last figures magnified. — Fig. 9, 10, 11. Eolidia Cu- 

 vierii, of the natural size. 



