HIRUDINEA AND OLIGOCH^TA OF THE GREAT LAKES REGION. 165 



/'. Dorsal seta; beginning on somite III, partly capillary, partly acicular in each bundle; 



prostomial process a short papilla Naidium sj>. (p. 166). 



//'. Dorsal seti« beginning on somite II, all capillary and those on III greatly elongated ; 

 except in the first two bundles the dorsal set« are roughened with minute spines; 



prostomial process a long, slender tentacle Prislina leidyi (p. 166). 



fff. Dorsal setse beginning on VI, exclusively capillary and smooth, and those on III not 

 materially longer than the others; prostofnium without lateral lobes and tapering 



regularly into the slender elongated tentacle Sti/laria /ossidaris (p. 167). 



ffff. Like S. fossularis, except that the prostoraium is provided with a pair of lobes, from 



the cleft between which the tentacular proboscis arises Slylaria lacustris (p. 167). 



ee. Prostomium rounded, without any produced process. 



g. Dorsal set» bundles present on all somites except the first five. 



h. Dorsal setie exclusively capillary, those on VI much longer than the others; 

 integumental sense papillae of large size and metameric; no expanded caudal 



plate Slai'ina gracilis (p. 167). 



hh. In addition to the capillary setae dorsal bundles contain some that are curved and 

 bifid or simply acicular, those on VI not longer than the others; no expanded 



caudal plate iWiis elinguis (p. 166). 



hhh. Dor.saV bundles composed of both acicular and capillary seta; not especially 

 elongated on VI; the caudal somite broadly expanded into a plate bearing 



marginal ciliated branchial processes Dero limosa (p. 167 ) . 



gff. Dorsal sette totally absent from all segments. 



!. Form elongated as in Nais, the prostomium well developed; only 2 or 3 setse in the 



ventral bundles Schmardaella JUifm-mis (p. 168 ). 



dd. Prostomium rudimentary and not distinct from peristomium; somite III much enlarged for 

 the accommodation of the large pharynx, which equals or exceeds the (jesophagus in 

 length; number of somites small, about 15 for the single zooid; ventral setfe totally want- 

 ing from somites III to V and dorsal setae absent from all somites. 



j. Length of living animal 10 to 15 mm.; the oesophagus short but distinct; habit 



free living Chsetogaster diaphanus (p. 168). 



jj. Length of living animal 2 to 4 mm.: the oesophagus very short and indistinct; 



usual!}- jjarasitic on water snails ChxlogaMer limnxi ( [). 169) . 



Size moderate or large; reproduction normally by the sexual method alone; alimentary canal often 

 complicated by the development of a crop, gizzard or other organs; aquatic, semiaquatic or 

 terrestrial. (Lumbriculidie, Tubiflcidie, Glossoscolecidse, and Lumbricidae. ) 



k. All setse hooked and bifid distally, more than 2 per bundle in the preclitellar 

 segments at least; a single pair of spermiducal funnels in X, 1 pair of sperma- 



thecae in X ; prostate glands elongated Lim nodridus gracilis (p. ] 69 ) . 



kk. All setae hooked and slightly bifid distally and arranged on all somites in 2 dor- 

 sal and 2 ventral pairs; 2 pairs of sperm funnels in somites IX and X; 5 pairs 

 of spermathecse in XI to XV or XII to 'S.Vl . . Tliiiiodrilus incoratans (p. 169). 

 kkk. Set« simple-pointed but slightly ornamented, arranged in pairs as in kk; 

 prostomium continuous with peristomium; clitellum extending from XIV 

 to XXVI; male pores on XIX; 3 pairs of spermathec^ in VI, VII, and 

 VIII; a pair of large glands in III; no muscular gizzard. 



SparganophilM eiseni (p. 170). 

 kkkk. Seta as in iii, but entirely without ornamentation; prostomium dovetailed 

 into peristomium from which it is separated at the sides by grooves; 

 clitellum beginning on XXV, XXVI, XXVII, or XXVIII, and ending on 

 XXXIII, XXXIV, or XXXV; male pores on XV; 2 pairs spermatheca; 

 in IX and X; gizzard well developed Helodrilus caliginosus (p. 171). 



