24 BULLETIN 168, UNITED STATES NATIONAL MUSEUM 



Description. — Body stout. Gray or blackish gray with unpig- 

 mented segment borders and clear rounded spots on the head and 

 the sides of the segments. Young individuals are gray, weakly pig- 

 mented. Eyes (pi. 5, fig. 50) three on each side, equal; eye spots 

 two on each side. The two anterior eyes on each side are close 

 together and occupy a single pigment spot; the posterior eye is remote 

 from these. Postantennal organ long, very narrow, bent, sometimes 

 notched. Antennae as long as the head, situated on a well-developed 

 antennal base; segments in relative lengths as 2:4:3.5:7:5. Sense 

 organ of third antennal segment typical. Fourth segment with an 

 apical rounded tubercle, a subapical papilla, and several long olfac- 

 tory setae. Last three abdominal segments ankylosed, with occa- 

 sionally a trace of a suture between the fourth and fifth segments. 

 Unguis (pi. 5, fig. 51) rather large, with small lateral teeth but \vithout 

 an inner tooth. UngLiiculus broadly lanceolate, with apex setaceously 

 prolonged, untoothed. Tenent hairs absent. Furcula appended to 

 the fourth abdominal segment, extending almost to the anterior 

 margin of the second abdominal segment. Manubrium rather slen- 

 der, with a strong subapical ventral seta and several fine dorsal setae. 

 Dentes one-fifth longer than manubrium, narrowing distally, dorsally 

 crenulate, the crenulations ceasing rather far from the mucro, wdth 

 several dorsal and ventral setae. Mucro conspicuously large, about 

 one-sixth as long as dens, bidentate, without subapical seta. Rami 

 of tenaculum quadridentate ; corpus with one seta. Clothing of com- 

 paratively short dense simple setae; outstanding sensory setae simple. 

 Maximum length, 2.1 mm. 



Remarks. — The preceding description is based on that of Linnaniemi 

 (1912) with the aid of specimens received from Dr. C. Schaffer. 



In the collembolan fauna there are few species that are so typically 

 Uttoral as this one. It occurs exclusively on the seashore under sea- 

 weed, moist stones, and pieces of wood near the edge of the water 

 (Linnaniemi). 



Distribution. — F. sexoculata is known from east Greenland, Jan 

 Mayen Island, Spitsbergen, Norway, Sweden, Denmark, Finland, 

 Germany, Switzerland, Great Britain, and Ireland. 



FOLSOMIA QUADRIOCULATA (Tullberg) 



Plate 5, Figures 52-58 



Isotoma quadrioculata Tullberg, 1871, p. 152; 1872, p. 48; 1876, p. 36. — 

 Stuxberg, 1887, p. 43.— Uzel, 1890, p. 66.— MacGillivray, 1891, p. 274; 

 1896, p. 58.— MoNiEz, 1891, p. 70.— Schott, 1894, p. 74; 1902, p. 21.— 

 VON Dalla Torre, 1895, p. 10. — Reuter, 1895, p. 28. — Lie-Pettersen, 

 1896, p. 18; 1898, p. 13; 1907, p. 60.— Meinert, 1896, p. 170.— Schaffer, 

 1896, p. 183; 1900a, p. 248; 1900b, p. 255.— Poppe and Schaffer, 1897, 

 p. 268.— Lubbock, 1898, p. 619.— Scherbakov, 1898a, p. 58; 1898b, p. 12.— 

 Gael, 1899, p. 310; 1901, p. 261.— Wahlgren, 1899b, p. 337; 1900a, p. 367; 



