304 



APPENDIX. 



foot in length ; and, as it had altered a little, the colour and the 

 entire smoothness of the species cannot be positively affirmed. But 

 Mr. Thompson's specimen, on which no alteration seems to have 

 been produced, was smooth all over the surface. It was 4 inches in 

 length. 



Pennant, in his description of the Basking Shark, says, — "The 

 fishers often observe on them a sort of leech of a reddish colour, and 

 about 2 feet long, but which falls off when the fish is brought to the 

 surface of the water, and leaves a white mark on the skin." — Brit. 

 Zool, iii. 139. 



Pontobdella campanulata (page 42). 



"Length, when extended, 13 lines; body round; diameter about 

 half a line. The anterior extremity dilates as a very broad disk, 

 somewhat like a flattened hand-bell ; the posterior extremity dilates 

 in the same manner ; sucker very large proportionably. Colour of 

 the body dark olive, finely speckled with yellow. Disk and sucker 

 very pale." — Balyell, p. 12. Extremely restless. 



Pontobdella littoralis (page 42). 



Body one inch in length and a line in diameter, slightly tapered 

 forwards, terminated at each end with a plain circular sucker, of a 

 uniform chestnut-brown colour, or red and mottled (for the colour 

 varies according to the intestinal contents), smooth, rather soft and 

 compressed in extension ; the margins minutely crenulate under a 

 magnifier. 



The segments are very obscurely marked, but they are divided by 

 circular lines which make the body appear crenulate under the mag- 

 nifier. The sexual pores are near the outer extremity, and a little 

 protuberant. 



Plate II. C. fig. 4. P. marina, of the natural size. 5. The same mag- 

 nified. 6. An outline figure drawn from au individual which had the 

 genital organs extruded. 



Hirudo vittata, — " Length above 2 inches ; breadth 3 lines ; 

 thickness 1 line ; body flattened, smooth upper surface, slightly 

 convex. Anterior extremity formed as a cup, occasionally flattening, 

 and applying like a disk to other substances ; posterior extremity 

 broad, thin, and large in proportion to the animal, employed as a 

 sucker. That of a very large specimen of the Hirudo vittata, one 

 extending 8 or 9 inches, was of smaller diameter. The body is 

 chiefly whitish and speckled, somewhat transparent, so as to expose 

 ten pairs of cells within. Ten projections, like hemispherical blisters, 

 border each side of the animal, rising and falling as if by respiration ; 

 no eyes could be found. — It generally remains erect on the broad or 

 adhering sucker, often waving to and fro." — Balyell, p. 9. 



The capsules are sessile, nearly hemispherical, about one-third of 



