10 BULLETIN 168, UNITED STATES NATIONAL MUSEUM 



Unguis without a tunica. Dentes very rarely tuberculate or 

 smooth dorsally; usually stout, though slender in a few species; 

 usually with dorsal transverse folds, few to many in number; 

 with large rounded dorsal lobes in a few species. Third uro- 

 tergite usually shorter than the fourth, the two rarely subequal. 

 Genital and anal segments ankylosed or not. Furcula not 

 attaining the ventral tube, as a rule. Manubrium often longer 

 than the dentes, rarely with many ventral setae; commonly 

 with one pair of ventral subapical setae; in a few species naked; 

 rarely with two, three, or four pairs of ventral subapical 



setae Proisotoma (p. 38) 



10. Abdominal fringed bothriotricha present. Mucrones lamellate, 



quadridentate, with a lateral seta Isotomurus (p. 70) 



Abdominal bothriotricha absent. Mucrones rarely lamellate .Isotoma (p. 78) 



Genus TETRACANTHELLA Schott 



Luhbockia Haller, 1880, p. 4. 



Tetracanthella Schott, 1891a, p. 191. — Borner, 1902a, p. 106. — Linnaniemi, 



1912, p. 100. 

 Deuterolubbockia von Dalla Torre, 1895, p. 14. 



Genotype. — Tetracanthella pilosa Schott. 



Eyes eight on each side. Postantennal organs of the isotomino 

 type elUptical, simple. Antennae 4-segmented. Fourth antennal 

 segment with terminal tubercle, subapical papilla, and usually 

 olfactory setae. Mouth parts mandibulate. Body elongate. Pro- 

 thorax much shortened. Genital segment enlarged; anal segment 

 reduced; anus ventral. Anal spines four (two in one species). Un- 

 guiculus present (or absent). Tenent hairs present (or absent). 

 Furcula present (or absent), short, not attaining the ventral tube, 

 Mucro ankylosed with dens (or not). Clothing of simple setae. 

 Integument reticulate, not tuberculate. 



The parenthetical qualifications given above apply to certain 

 European species of the genus. 



Tetracanthella combines achorutine with isotomine characters, with 

 the latter predominant. Its strongest affinities are with Anuro- 

 phorus. (On this subject see Borner, 1902a, 1903, 1906.) 



TETRACANTHELLA WAHLGRENI Axelson 



Plate 1, Figures 1-9 



Tetracanthella pilosa Schott, 1891a, p. 192 (part); 1894, p. 77 (part); 1902, p. 18 

 (part).— Lie-Pettersen, 1896, p. 19. — Wahlgren, 1899b, p. 336; 1900b, 

 p. 5; 1906b, p. 248.— Axelson, 1900, p. 111. 



Tetracanthella coerulea Schaffer, 1900a, p. 245; 1900b, p. 251. 



Tetracanthella wahlgreni Linnaniemi (Axelson), 1907, p. 80; 1912, p. 103. — 

 Bagnall, 1914, p. 7. — FoLSOM, 1919a, p. 7; 1919b, p. 275. — Wahlgren, 

 1919, p. 750.— Remy, 1928, p. 64.— Handschin, 1929, p. 56. 



Description. — Dark blue. Body elongate, narrowing posteriorly 

 (pi. 1, fig. 1). Eyes (pi. 1, fig. 2) eight on each side, on black patches; 

 the two inner posterior eyes of each side smaller than the others; the 



