496 Illinois State Laboratory of Natural History. 



is everywhere roughened by projecting cutaneous sense 

 organs. 



The anterior metameric sensillfe (PI. XLIL, Fig. 6) are very 

 difficult to make out in surface views, but about X or XI they 

 become very conspicuous and continue so to the posterior end. 

 Here they appear as eight dorsal series of clear white spots. 

 The dorso-medians (md) are placed on each side of the median 

 papillae, separated by a distance about two thirds of that which 

 intervenes between them and the dorso-laterals. The latter 

 (dl) are just about half-way between the mesion and the 

 margins, or a trifle nearer to the latter, and consequently are 

 external to the dorso-lateral papillae. The dorso-marginals 

 {dm) are well back from the margins, being about as far from 

 the dorso-laterals as are the dorso-medians, except on the 

 incomplete somites, where the former distance is less. The 

 supra-marginals (sm) are very minute and on the exact 

 margins as viewed from above, except on the incomplete 

 posterior somites, on which they are somewhat removed from 

 the margins. The ventral sensillse have not been studied. 



Reproductive Organs. — In most respects resembling the 

 species of Placobdella the reproductive organs differ from 

 theirs and resemble those of G. complanata in one important 

 feature : the enlarged portion of the sperm-duct (epididymis 

 and ductus ejaculatorius), instead of simply coiling up, extends 

 caudad in a long straight loop which lies ventrad to the gas- 

 tric caeca and reaches at least as far as ganglion XV. 



Alimentary Canal. — The proboscis is of relatively much 

 greater diameter than in the two species of Placobdella 

 described, and the gastric caeca are of small size and scarcely 

 lobed. There are but six pairs of these caeca, which increase 

 in size caudally, and the first of which (in XIV) is rudi- 

 mentary or sometimes absent. In all of these respects this 

 species is intermediate between G. complanata and G. 

 stagnalis. 



Color. — The colors are here described from preserved 

 material. They are very simple and effective. Below, a 

 plain ash-color; above, the same color marked by eleven or 

 twelve longitudinal stripes of brown which are further com- 



