84 THE LEECHES OF MINNESOTA 



Genus Placobdella R. Blanchard. 



Body widened and moderately or excessively depressed. Suck- 

 ers variable, the caudal sometimes with minute marginal serrations. 

 Eyes usually one pair, compound, on somite III, rarely followed 

 by several pairs of imperfect simple eyes. Cutaneous papillae vari- 

 able, but usually numerous and some median. Pharyngeal salivary 

 glands large and compact; gastric caeca seven pairs, very large and 

 much branched in the flatter species. Sperm ducts without loops, 

 compacted and much convoluted. Parasitic on turtles, fishes and 

 batrachians, or free-living. 



Placobdella parasitica (Say) Moore. 

 (Plate I, figs. 7, 8) 



Hirudo parasitica Say (1824) 

 Glossiphonia parasitica Castle (1900) 

 Placobdella parasitica Moore (1901) 



Description — Of all of our numerous species .of glossiphonids 

 this attains the largest dimensions. Ordinarily examples are about 

 two inches in length when extended, the giants upwards of four 

 inches in the same condition. The form is broad, very flat and 

 foliaceous particularly when food is absent from the cseca. In ex- 

 tension the head is somewhat expanded, but in contraction partakes 

 of the general ovate pyriform outline of the body. The posterior 

 sucker is of large size and considerably exposed behind the body, 

 the plane of its adhesive surface being parallel with the ventral 

 surface of the body. Cutaneous papillae are numerous but incon- 

 spicuous, low and smooth ; sometimes they are obsolete. The most 

 constant are disposed in three longitudinal series on the neural 

 annuli and two longitudinal series on the post-neural annuli. Those 

 of the median series are not enlarged but on the contrary are usually 

 smaller than those of the paired series. 



The annuli and the somite limits are well defined, the furrows 

 exhibiting certain constant differences in depth. Somites I and II 

 are united in the reduced prostomial lobe, which may, but usually 

 does not present a faint cross furrow; III and IV r are triannulate, the 

 anterior annulus in each case being much the larger. Somite V is trian- 

 nulate dorsally but the furrow ai/as is faint and becomes obsolete on 

 the ventral side. There is a very gradual deepening of the furrow 

 a i /a j on the succeeding somites, but VI to XXIII or sometimes 



