I20 KKSK ARCHES IX HKI.MINTHOLOGV AND PARASITOLOGY. 



leech, its long and frequent employment in the medical profession, 

 and the vast numbers which have been brought to notice, it has 

 been so imperfectl}- described that, in the excellent Systema Hel- 

 minthum of my late esteemed friend, Dr. Diesing, of Vienna, it has 

 been placed with the " Bdellidea species genere penitus dubiae." I 

 therefore take the present opportunitj^ of indicating its characters 

 more fully. It agrees most nearly with the diagnosis of the genus 

 Hirudo, of which the H. rnedicinalis is the type, but nevertheless 

 possesses peculiarities perhaps rather more than specific. Its char- 

 acters, generic and specific, are as follows : 



Hi rudo Decora. Say: Long's Expedit., vol. ii, 1842, Append., 

 268. Moquin Tandon : Monog. Hirud., 1846, 344. Diesing : Syst. 

 Helm. , i, 1850, 474. Wood and Bache : United States Dispensatory. 



Body elongated, compressed cylindroid, narrowing anteriorly, 

 laterally sub-acute ; in motion convex above, flat below, with the 

 margins compressed, thin, acute, and somewhat wavy ; composed of 

 from 90 to 94 annuli, which are uniform and smooth. Head con- 

 tinuous with the body. Mouth obliquely terminal, bilabiate ; the 

 upper lip prominent, semiovate, obtuse, or from contraction of the 

 lip emarginate ; lower lip forming the inferior portion of the first 

 annulus ; the lips together acting as an acetabulum ovoid or obcor- 

 date in form. Eyes 10, arranged in horseshoe form, the anterior 8 

 above the upper lip, the posterior pair separated from the others by 

 the first annulus. Acetabulum subbasilar, ventral, .sessile, circular. 

 Anus dorsal, above the acetabulum. Male aperture perforating the 

 25th annulus, with the lips more or less prominent. Female aper- 

 ture between the 29th and 30th annuli. A group of four papillae 

 situated back of the latter on the 34th to the 36th annuli inclusive. 

 Jaws three, semicircular, laterally compressed, furnished with 55 

 teeth, which have an acute curved summit and an expanded bilobed 

 base. (Esophagus short and narrow compared with that of Aiilas- 

 to)nu»i, furnished with 6 longitudinal folds, of which three coarse 

 ones descend from the jaws and three narrow ones are intermediate. 



Co/or. — Dorsal surface olive green, with a median irregular band 

 and a lateral line of darker hue of the same kind ; a median row of 

 reddish brown dots, and a lateral row of black dots. Ventral sur- 

 face reddish brown, extending slightly above the lateral margin, 

 devoid of spots, or more or less maculated with black. Acetabulum 

 colored like the back above and the belly below. 



In the genus Hirudo, as characterized by Diesing (Syst Helm., i, 

 465), and to which he assigns 9 recognized species, the jaws are 

 furnished with from 60 to 70 teeth, and the male aperture is situated 



