468 , ANNELIDES. 



three folds of skin. Several small species are found in the stagnant 

 waters of Fraucej it is thought proper to distinguish from them the 



Trochetia, Dutroch.(l) 



Which only differs from them in an inflation at the spot where 

 the genital organs are placed. 



One species is found in France Geobdella trochetii, Blainv., 

 Diet, des Sc. Nat., Hirud., pi. IV, f. 6, which frequently leaves 

 the water in pursuit of Lumbrici. 

 M. Moquin-Tandon, under the name of Aulastoma, even de- 

 scribes a subgenus, where the mouth is merely furnished with 

 numerous longitudinal plicse Jlulast. nigrescens, Moq. Tand., pi. 

 vi, f. 4. 



Immediately after the Nephelides come the Branchiobdella, 

 Odier, remarkable for their two jaws and the absence of eyes. 



One species is known Avhich lives on the branchiae of the 

 Astaci(2). 

 In all these subdivisions the anterior sucker is but slightly sepa- 

 rated from the body; in the two following ones it is clearly distin- 

 guished from it by a strangulation, is composed of a single seg- 

 ment, and has a transverse orifice. In the 



HiEMocHARis, Sav.(3) 



In addition to this conformation, there are eight eyes, a slender 

 body, and but slightly distinct rings. The jaws are salient, and 

 scarcely visible points. The Haemochares do not swim, but walk 

 like the caterpillars called Geometrae, and adhere particularly to 

 fishes. 



One species, Hirudo piscium, L. j Roesel, III, xxxii, is fre- 

 quently observed on the Cyprini(4). The 



Helluo. Such are : Hir. vulgaris, L., or H. odoculata, Bergm., Stock., Mem., 

 1757, pi. vi, f. 5 8; N. atomaria, Caren., L., C, pi. xii. See also pi. vl of Moquin- 

 Tandon. 



(1) M. de Blainville changes this name to Geobdella. 



(2) Branchiobdella Astaci, Od., Mem. de la Soc d'Hist. Nat. de Paris, t. I, 

 pi. iv. 



(3) M. de Blainville, who had named them Piscicotjs, a name adopted by La- 

 marck, has again changed it to Icthxobdella. 



(4) Add, Pisdcola cephalota, Caren., pi. xii, f. 19, and Moq. Tand., pi. yii,f. 2; 

 Piscic. tesselata, Moq. Tand., f. 3. 



