NAIS. CH^TOGASTER. 71 



9. NAIS. 



Nais, Lam. An. s. Vert. iii. 222. Leach in Supp. Encyclop. Brit. i. 

 451. Ehrenberg in Lam. An. s. Vert. 2de edit. iii. 612. Oersted 

 in lib. cit. 135. 



Char. Body linear, subcylindrical, acuminate in front, truncate 

 behind : head (= the three or four first segments) continuous with 

 the body, not produced : eyes 2 or none : superior bristles capillary 

 (sometimes uncinate), the inferior forked. 



1. N. scotica, bristles shorter than the diameter of the body, fas- 

 ciculate. Length 1". 



Nais lacustris, Dalyell, Pow. Creat. ii. 130. pi. 17. f. 1-5. 



Hab. At the roots of subaquatic plants. 



Desc. " Length an inch ; body round ; extremities obtuse ; the 

 anterior smooth and cylindrical, the portion behind it provided with 

 a double row of thin tufts of prickles, some of them composed of 

 several bristles. The extremities contain the mouth, and the termi- 

 nation of the excretory canal." "The mouth seems a dilatable 

 cylinder without a proboscis." — Dalyell. 



2. N. filiformis. 



Nais filiformis, Williams in Rep. Brit. Assoc. 1851, 182 & 263. 

 Hab. Freshwater pools, abundant. Dr. Williams. 



Obs. I cannot say whether this is a new species, or a Miillerian 

 one under a new name. There is no description. 



10. CH^TOGASTER. 



Chaetogaster, Baer in Nov. Act. Curios, xiii. (1826). Oersted in 

 Kroyer's Naturh. Tidssk. 1843, 138. Zool. Journ. iv. 258. 



Char. Body cylindrical, tnmcate in front : eyes none : mouth 

 terminal, barbed underneath on the first segment : bristles all spinets 

 forked at the apex. 



1 . Ch. vermicularis. 



Nais vermicularis, Miill. Verm. i. ii. 20. Turt. Gmel. iv. 91 ; Brit. 



Faun. 137. Stew. Elem. i. 390. Penn. Brit. Zool. iv. 97 (1812). 



Lam. An. s. Vert. iii. 223 ; 2nde edit. iii. 674. Templeton in Loud. 



Mag. Nat. Hist. ix. 235. Dugh in Ann. des Sc. nat. viii. 30 (1837), 



pi. 1. f. 21, 22. 

 Nais diaphana, Gruithuisen in Zool. Journ. v. 380. 

 Chsetogaster Limnei, Bder in Nov. Act. Curios, xiii. tab. xxix. f. 23. 

 Chsetogaster diaphana. Oersted, lib. cit. 138. pi. 3. f. 2, 15 & 17- 

 Chaetogaster vermicularis, Grube. 



Hab. Amongst Lemnee in ditches. 



Obs. Body cylindrical, hyaline, 10-12'" in length, of eighteen to 



