NEW NORTH AMERICAN EARTHWORMS 165 



anteriorly and posteriorly are approximately aa:db:'bc:cd= 

 14 : 3 : 8 : 6 ; fZiZ anteriorly is nearly two-thirds of the circumference 

 and posteriorly only about one-half of it. The penial setae are very 

 closely approximated on each side of 18 and also very close to the 

 male pores, which are slightly laterad of h. The sectioned penial 

 setae were in fragments, but the length is evidently more than 1.5 

 mm and the diameter 0.035-0.04 mm. There is an abrupt curve near 

 the distal end, but elsewhere the setae were apparently nearly 

 straight. The terminal parts are minutely sculptured. The clitel- 

 lum is incomf)lete ventrally and includes 13-20. Paired ventral 

 papillae are present on 15/16, 16/17, 19/20, and 20/21. 



Dorsal pores are present posterior to the clitellum. Nephridio- 

 pores are very inconspicuous and situated near the anterior margins 

 of the somites. The male pores are paired on 18 slightly laterad 

 of seta line &, and the protruding penial setae are in paired de- 

 pressions of the ventral surface. Oviducal pores are paired on 14. 

 Spermathecal pores paired on 7/8 and 8/9 in seta line 6. 



Intei^iaZ characters. — Septa 6/7-11/12 are most thickened. A lack 

 of sections of the anterior dozen somites accounts for a lack of de- 

 tails concerning some of the organs of those somites. A tliick-walled 

 pharynx is followed by a powerful gizzard in 5. The sectioned part 

 of the esophagus posterior to the middle of 13 has the type of struc- 

 ture termed calciferous gland but is of the simpler type such as is 

 found in M. americanus. The lining layer of the lumen forms nu- 

 merous irregularly arranged elongate diverticula, which are of vari- 

 able length, and many extend nearly two-thirds of the way to the 

 middle of the lumen. They receive an abundant blood supply from 

 the vascular plexus in the esophageal wall. An examination of the 

 alimentary tract in the unsectioned region reveals a gradual increase 

 in diameter and in the number and length of the diverticula in 10-13. 

 The differentiation of this part of the esophagus as a calciferous 

 gland is even less than that found in M. ainerlcanus. In 16 and 17 

 the lining layer forms longitudinal folds not extending far into the 

 lumen. The folds become fewer in number in the following somites, 

 and then the enlarged intestinal tract begins at about the twentieth 

 somite. A definite typhlosole is present. 



The circulatory system has not been thoroughly studied but seems 

 similar in essentials to that in the other species here described. Three 

 pairs of smaller hearts are present in 7-9, and four pairs of larger 

 hearts are present in 10-13. The pair in 13 are the only ones of which 

 sections were made, and they are of the dorso-esophageal type, open- 

 ing into the ventral vessel below, and dorsally each of them has a 

 small branch that opens into the dorsal vessel and a larger one open- 

 ing directly into the esophageal vascular plexus. It seems probable 



104264—36 2 



