Smith — Lake Superior Lumbriculids. 35 



Mesoporodrilus asymmetricus F. Smith. 



Length, 30 mm. Diameter, 0.5 mm. Somites, 65. Pale; without pig- 

 ment. Prostomium prolonged into tentacle-like extension. Setae closely- 

 paired; simple. Clitellum, H9-J^13. Spermathecal pores median; two 

 on 9. Spermaries and spermiducal funnels paired; in 10. Diameter of 

 reservoir one and one-half times that of its lumen. Spermathecae, two; 

 in same side of 9; sacs may extend into adjacent somite. 



Holotype. — Cat. No. 27,235, Illinois State Laboratory of Natural History. 

 Type locality, Quiver Lake, near Havana, Illinois. 



Mesoporodrilus lacustris (Verrill) F. Smith. 



Length, 42 mm. (?) Diameter about 1 mm. Somites, number un- 

 known. Setae closely paired; simple. Clitellum on 9-12 and encroaching 

 on 13. Spermathecal pores median; on 9, or on 8 and 9 Spermaries 

 and spermiducal f unn els paired; in 9 and 10. Sperm ducts, two pairs; 

 all opening into the single sperm reservoir near its posterior end. Diameter 

 of reservoir three times that of its lumen. Spermathecae, one, or two; 

 asymmetrically disposed; each with elongated duct opening on 9, or on 

 8 and 9; and sac with thick wall, in the same or in adjacent somites. 



Cotypes.— Cat. No. 15,589, U. S. N. M.; Cat. No. 17,947, U. S. N. M. 

 (Lectotype, Cat. No. 15,589, U. S. N. M , selected by F. Smith). Type 

 locality: Lake Superior, south side of Saint Ignace Island. 



The specimens show evidence of maceration and are more or less frag- 

 mentary. There are no complete specimens permitting observation of 

 length and number of somites. The specimen which serves as type for 

 this description is one of the cotypes mentioned above; it includes fifteen 

 anterior somites, and is cut into transverse sections. Transverse and 

 sagittal sections were made from specimens from the other collection which 

 are used as paratypes. 



External Characters. 



The maximum diameter (1 mm. or slightly more) is in the clitellar 

 somites and considerably exceeds that of the accompanying Lumbriculus 

 specimens. The color of the living worms is unknown, since the "reddish 

 brown" of Verrill's description may or may not apply to this species. 

 The prostomium has very thin walls near the end; is incomplete in each 

 specimen studied; and in living specimens may terminate in a tentacle- 

 like extension, as does that of M. asymmetricus. The setae are slender 

 and very similar in form to those of the last named species (Smith, 1896, 

 fig. 9). The nodule is one-third of the length, from the distal end, and the 

 outer third is more strongly curved. Ventral setae of the clitellar somites 

 are about 0.225 mm. long and the diameter near the nodule is about 

 0.011 mm. Other setae are somewhat smaller. The relative distances 

 between the pairs are approximately indicated by the formula: aa= 

 j^bc= T \dd. The clitellum is chiefly confined to somites 9-12, but en- 

 croaches slightly on 13. The spermiducal pore is on the summit of a small 

 median papilla near the posterior border of 10. The oviducal pores are 



