AMPHIPORUS LACTIFLOREUS. 157 



1862. Ommatoplea mutabilis, Diesing. Revision der Turbell., p. 257. 

 „ „ violacea, Ibid. Op. cit., p. 257. 



„ „ berea, Ibid. Op. cit., p. 257. 



„ „ glauca, Ibid. Op. cit., p. 25 7, bis. 



„ „ alba, Ibid. Op. cit., p. 257. 



„ Nemertes mandilla, Ibid. Op. cit., p. 303. 



„ Borlasia mandilla, Keferstein. Zeitsch. fiir wiss. Zool., Bd. 12, p. 58, Taf. 5, f. 1 — 7. 



1863. Ditactorrhochma mandilla, Diesing. Nachtrage zur Revis. der Turb., p. 11. 



1865. Omatoplea rosea, Johnston. Catalogue Brit. Mus., p. 23, pi. Ha, I 2, 2* 2** 3, and 3*. 

 „ „ alba, Ibid. Op. cit., p. 23. 



1865-6. Polia mandilla, De Quatrefages. Hist. Nat. des Anneles, pi. 4, f. 3. 



1866. Ommatoplea rosea, Lankester. Ann. Nat. Hist., 3d Ser., vol. xviii, p. 388. 

 „ „ alba, Ibid. Op. cit., p. 388. 



1867. „ „ Mcintosh. Bept. Brit. Assoc., 1867 ; Trans. Sect., p. 92. 



1868. „ „ Ibid. Ann. Nat. Hist., 4th ser., vol. ii, p. 293. 



1869. „ „ and var. rosea, Mcintosh. Trans. Roy. Soc. Edinb., vol. 25, pt, ii, p, 323 



et seq. 



Habitat. — Under stones between tide-marks and in the laminarian region; abundant. 

 Generally distributed — from the Arctic Seas probably to the Mediterranean. 



Body rounded on the dorsal surface, flattened on the ventral, not much tapered towards the 

 tail, which is rather blunt. In newly spawned specimens the body is much flattened, but in 

 those bearing ova it is rounded. Length one to three inches, and occasionally even reaching 

 four inches ; breadth three lines. 



Colour.— Various shades of white or pinkish white, with a translucent streak along the centre 

 of the dorsum — caused by the proboscidian chamber. Specimens with the generative organs well 

 developed assume a grayish aspect. There are two conspicuous pink or reddish-pink spots indi- 

 cating the ganglia in front. The under surface has the same colour as the dorsum, and during 

 the quiescent state of the reproductive organs is distinctly marked by the pinnse of the digestive 

 chamber. A specimen found at St. Peter Port, Guernsey, had the body of a pale greenish hue, 

 like that usually seen in Tetrastemma melanocephala ; while in the Bight of Vatsland (to the north 

 of Bressay Sound) in Shetland a variety with the pigment everywhere increased abounds on a 

 sandy bottom. 



Head spathulate, flattened, and slightly pointed ; furnished with numerous eyes placed in 

 two or three groups on each side, the anterior generally forming a marginal row ; the posterior 

 arranged in front of or sometimes over the ganglia, and three often forming a triangle. In the pale 

 brownish variety from Shetland an eye-speck on each side in front of the ganglia is larger and more 

 conspicuous than the others. 



Cephalic furrows. — Midway between the tip of the snout and the anterior border of the 

 ganglia a furrow runs inwards and slightly forward on the dorsum, ceasing before it reaches the 

 middle line. On the ventral surface is a similar though shorter furrow, the two meeting on the 

 side at a richly ciliated dimple, which leads into the cephalic pit. A short distance behind the 

 ganglia two other superficial furrows exist, each slanting backwards and inwards to meet its 

 fellow of the opposite side in the middle line. These furrows are also continued inferiorly, but 

 with a slightly altered direction, so that they meet under the ganglia. The two sets of furrows 

 are indicated in the flattened head by lateral notches. 



