96 BULLETIN 168, UNITED STATES NATIONAL MUSEUM 



Fourth antennal segment without special olfactory setae, with three 

 unequal apical tubercles, and subapical pit with papilla. Unguis 

 (pi. 31, fig. 357) rather narrow, feebly curving, with a pair of evident 

 lateral teeth; inner margin un toothed or with a weak tooth one- 

 third from the apex. Unguiculus extending two-thirds as far as the 

 unguis, broadly lanceolate, acuminate, with inner lamella broadly 

 rounded and untoothed. Tenent hairs absent; in place of these a 

 long simple seta. Abdominal segments without ankylosis (pi. 31, 

 fig. 358). Third abdominal segment slightly longer than the fourth 

 (about as 37:35). Furcula appended to the fifth abdominal segment, 

 and extending to the middle of the second. Manubrium with many 

 dorsal and ventral setae. Dentes a little more than twice as long as 

 manubrium, slender, gradually tapering, dorsally crenulate except 

 basally and apically. Dens without a long subapical seta. Mucrones 

 five-sevenths as long as hind unguiculi. Mucro (pi. 31, figs. 359, 360) 

 quadridentate; apical tooth exceptionally long, slender, projecting 

 obliquely upward and more or less hooked ; anteapical tooth smaller, 

 conical, erect or slightly inclined; proximal teeth smallest, subequal, 

 almost side by side, one of them being lateral and more or less oblique. 

 Rami of tenaculum quadridentate; corpus with many ventral setae 

 (about 11 to 17). Clothing (pi. 31, fig. 361) of dense short simple 

 setae; sensory setae short, erect, simple, in a row across the middle 

 of each body segment except the prothorax, and becoming long on 

 the genital and anal segments. Maximum length, 1.7 mm. 



Remarks. — The inner tooth of the unguis is commonly absent, and 

 when present is small. 



The specimens that I have seen from this country have no angle- 

 tooth on the unguiculus, there being at most a suggestion of a tooth; 

 though such a tooth is usually present in European specimens. 



As a variation, the apical tooth of the mucro may be stouter than 

 usual. 



My determination of this species is based on an examination of 

 Packard's types in the Museum of Comparative Zoology, Cambridge, 

 Mass. The types studied were three from Brunswick, Maine, those 

 from Salem, Mass., being absent from the collection. 



I sent Massachusetts specimens to Dr. C. Schaffer, who reported 

 (Schafi'er, 1900b) that his nivea was synonymous with albella Packard. 



A specimen of albella from Finland, which I received from Dr. 

 Linnaniemi, agrees essentially with our examples of the species. The 

 specimens described by Linnaniemi (1912) as compared with ours 

 have a narrower postantennal organ, stouter unguis with the tooth 

 near the middle of the inner margin, shorter unguiculus with an 

 evident tooth, and relatively longer third abdominal segment. 



Specimens from Poland, received from Dr. Jan Stach, agree with 

 North American material of tliis species. 



