508 Illinois State Laboratory of Natural History. 



The distances separating the two dorso-medians and the dorso- 

 laterals from the dorso-marginals are about equal and some- 

 what less than that between the dorso-medians and dorso- 

 laterals. 



XXV exhibits very much less distinct secondary furrows, 

 the annuli all of about equal size, and the somite prac- 

 tically triannulate. This is also the last somite to bear 

 distinct papillae. 



XXVI is strictly triannulate, with the sensillae on a 2, 

 but lacking any distinct papillae and secondary furrows. In 

 the figure, XXVII is represented as divided into three narrow 

 rings, but owing to a distortion of this region it is quite im- 

 possible to make a satisfactory determination. In some 

 lights and positions there appear to be three rings here, in 

 others two, and two drawings made at different times and 

 independently illustrate the two interpretations. 



The color has faded to a uniform gray. Nothing of the 

 internal organization could be learned by studying the speci- 

 men, either stained or unstained, in various clearing media, 

 and consequently this description leaves much to be desired. 

 The position of the ganglia and lateral nerves was deter- 

 mined by a partial dissection of the mid-ventral region of 

 two somites. 



HIRUDINTD.ffi. 

 Macrobdella Yeerill. 



Macrobdella decora (Say) Verrill. 



Hirudo decora Say ('24). 

 Hirudo decora Leidy ('68). 



Diagnosis. — Copulatory glands opening by four pores 

 arranged in a quadrate figure on XI I lb 6 and XIV b 1 and /; 2 ; 

 male pore at XI/XII or XII b 1, female, at XI I/XI 1 1 or XIII 6 

 1 ; somite XXVI has annuli (a 1 -j- a 2) + a3 ; annuli VII a 3 

 and VIII a 1 relatively large and partly subdivided dorsally ; 

 atrium short and spherical ; alimentary canal with exten- 

 sively developed caeca; denticles small, about 65 on each jaw, 

 and monostichodont ; color pattern metameric. 



