343 



Of this species, belonging to the so-called caelebs group, only the female 

 has so far been taken. 



Type.'— A female from Middlesex Fells, Mass., is in the collection of the 

 Boston Society of Natural History (Crust. 1144). Cotypes are in the author's 

 collection (Ml 96). 



Occurrence. — This species has been taken in damp, shady- 

 places, under stones or the decaying leaves and wood of decidu- 

 ous trees. It avoids exclusively coniferous woods. It is dis- 

 tinctly gregarious. 



Distribution.— -Maine: Mount Desert Island (Biol. Surv. Mt. 

 Desert Region),? Westbrook (Norton 1909, p. 251, as T. pusillus) ; 

 Mass.: Middlesex Fells (type locality), Boston, Forest Hills, 

 Sharon, Woods Hole, Nantucket. 



Remarks. — The simultaneous examination of specimens from 

 several localities has enabled me to form an idea of the range of 

 variation shown by the pleopods in this species and to supplement 

 the characters noted above. 



Pleopod I. The scales on the lateral portion of the basis are 

 sharply pointed. (Compare this with Miktoniscus halophilus, 

 p. 345.) The exopod is very constant in outline, with the pos- 

 terior margin slightly convex and the posterior margin distinct 

 and about half as long as the medial. The setae at the postero- 

 medial angle are variable, even entirely wanting. The endopod 

 is marked by its triangular form with the medial margin sagittal, 

 not oblique, and forming a distinct postero-medial angle. 



Pleopod II. The scales on the lateral portion of the basis are 

 again sharply pointed. The tip of the lobe is provided with a 

 few setae. The basal lateral margin has about six scales standing- 

 out from the margin at right angles to it. The endopod barely 

 exceeds the medial margin of the exopod. The exopod has the 

 posterior margin slightly concave. The lateral margin is two- 

 thirds as long as the medial. The spine at the postero-medial 

 corner is not always present. 



Pleopod III. The exopod is nearly rectangular with the pos- 

 terior margin slightly concave. One prominent spine is always 

 present at the postero-medial corner and a second, smaller spine 

 sometimes occurs just lateral to it. The endopod, excluding the 

 lateral lobe, is subtriangular, crenate on both free margins. 

 A marked indentation, of variable size, is present on the lateral 



