434 Dr. Johnston’s Index to the British Annelides. 
Templeton in Loud. Mag. N. Hist. ix. 236. Drummond in ibid. 
ix. 241. Johnston in ibid. ix. 355. fig. 52. Encyclop. Brit. xi. 226. 
2. G. argillaceus. 
Gordius argillaceus, Linn. Syst. 1075. Turt. Gmel. iv. 57. Turt. 
Brit. Faun. 130. Stew. Elem. ii. 353. Penn. Brit. Zool. iv. 73. 
Flem. Phil. Zool. ii. 605. 
Obs. Dr. Fleming says this “is only a variety’ of the preceding. 
I know of no description of it taken from British specimens. Species 
of Filarie have been frequently described as Gordit. 
Family PLanariaD&. 
Des Planaires, Cuv. Reg. Anim, iii. 266.—Mollusca Parenchymata, 
Swainson, Malacology, 35. 
Subfamily Linine. 
Borlasia. 
Borlasia, subgenus, Johnston in Mag. Zool. and Bot. i. 536. 
1. B. rufifrons. 
Nemertes B. rufifrons, Johnston in Mag. Zool. and Bot. i. 538. pl. 18. 
fig. 5. 
2. B. purpurea. 
Nemertes B. purpurea, Johnston in hb. cit. 1. 537. pl. 18. fig. 3. 
3. B. alba. 
Borlasia ? alba, W. Thompson’s Report, p. 271 ; and in Ann. Nat. 
Hist. xv. 320. 
4. B. octoculata. 
Nemertes B. octoculata, Johnston in lib. cit. i. 537. pl. 18. fig. 2. 
Planaria octoculata, Johnston in Zool. Journ. iv. 56. 
5. B. olivacea. 
Nemertes B. olivacea, Johnston in lib. cit. i. 536. pl. 18. fig. 1. 
Planaria bioculata, Johnston in Zool. Journ. iv. 56. 
6. B.? filiformis. Plate XV. fig. 1, a, b. 
Planaria filiformis, Johnston in Zool. Journ. iv. 56. 
Desc. Body very slender, elongate, about the thickness of common sewing 
thread, of a uniform white or yellowish white colour, soft, smooth, con- 
tractile, thickest in front and subcylindrical, tapered insensibly backwards 
and flattened : mouth terminal, sometimes protruded like a papilla: eyes 
none: anus terminal. Under a magnifier the sides appear minutely cre- 
nulate: the skin is transparent, and the centre dusky from a straight intes- 
tine which runs from one extremity to the other, and has on each side of it a 
series of oblong cells so closely approximated that they might seem almost 
to be formed by the convolutions of a single vessel. 
When lying at ease and contracted, this worm is from 1 to 2 inches in 
length, but it can, and does often voluntarily, extend itself until it is upwards 
of 6 inches, when it becomes a mere thread-like white line. In this state, 
the anterior extremity, from being obtuse, is thrust out into a needle-like 
point. It lives under stones, in muddy places, between tide-marks. 
