ÅR Class Arachnida consists, as is known, of a tolerably 
great number of higher Groups, Orders and Suborders, which 
are, in general, separated by exceedingly sharp characterist- 
ics; transition-forms from one of these groups to another 
are therefore rarely met with. Some of them, as the Phry- 
norde, the Thelyphonoide and the curious genus HKoenenia, 
GRASSI, consist of only a small number of species, or perhaps 
sometimes of a single species, and are so isolated, that it is 
difficult to assign to them their true rank within the Class; 
whereas other equally small and isolated groups, whose syste- 
matical place and nearest relations are easily recognised, 
differ from these in what might be believed to be their most 
essential characters. The Opiliones, or Harvest men, have, 
and with reason, been considered as one of the best charac- 
terized ÖOrders of Arachnida; it contains, however, a few 
groups which in a startling way deviate from the more typi- 
cal forms of the Order. Leaving aside the too imperfectly 
known genus Gibbocellum, STECK., which is by STECKER,' 
SÖRENSEN ” and others considered to belong to the Opiliones, 
but has by me” and by ÖCRONEBERG " been referred to the 
Chelonethi or Pseudoscorpiones, we have within that Order 
two families, the Stylocelloide (= Sironoidw?) Thor., and the 
Cryptostemmoide, WEstW., which form the types of two groups 
that differ widely from the rest of the Order and from each 
' Ueber eine neue Arachnidengattung aus der Abtheilung der Arthro- 
gastren, in Sitzungsber. d. k. böhmischen Gesellsch. d. Wissensch., Hft 6, 
1875, p. 239 et seq.; — Anatomisches und histologisches iiber Gibocellum, 
eine neue Arachnide, in Archiv f. Naturgeschichte, Bd. XXXXII, p. 293 
et seq. 
? Opiliones Laniatores Musei Havniensis, in Naturhistorisk Tidsskrift, 
Ser. III, XIV, p. 560 et seq. 
3 Descrizione di alcuni Aracnidi inferiori 'dell'Arcipelago Malese, 
in Annali del Museo Civico di Storia Nat. di Genova, XVIII (1882), p. 22 
(6) et seq. 
t Beitrag zur Kenntniss des Baues der Pseudoscorpione, in Bull. de la 
Soc. Imp. d. Naturalistes de Moscou, Nouv. Sér., II (1888), p. 459. 
