434 Dr. Johnston's Indeoc to the British Annelides. 



Templeton in Loud. Mag. N. Hist. ix. 236. Drummond in ibid, 

 ix. 241. Johnston in ibid. ix. 355.%. 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. 



Fiem. 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 Filarice have been frequently described as Gordii. 



Family Planariad^. 



Des Planaires, Cuv. R^g. Anim. iii. 266. — Mollusca Parenchymata, 

 Swainson, Malacology, 35. 



Subfamily Linince. 

 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. pi. 18. 

 fig. 5. 



2. B. 'purpurea. 



Nemertes B. purpurea, Johnston in lib. cit. i. 537. pi. 18. fig. 3. 



3. B. alba. 



Borlasia i 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. pi. 18. fig. 2. 

 Pianaria octoculata, Johnston in Zool. Journ. iv. oQ. 



5. B. olivacea. 



Nemertes B. ohvacea, Johnston in lib. cit. i. 536. pi. 18. fig. 1. 

 Pianaria bioculata, Johnston in Zool. Journ. iv. bQ. 



6. B. } filiformis. Plate XV. fig. \, a,b. 

 Pianaria 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- 

 Diilate: 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. 



