Cowparifio)! bcfirccii the MoKfli in Rlciunlci and Oxopoei 129 



therefore quite natural that we should here find a labium sternale', which is firmly chitinized, 

 long, and, except at the base itself, very narrow ; when the mandibles are closed the labium 

 forms the bottom of the mouth, as it generally does where it exists, and the narrow part of 

 the labium is then seen as a narrow band between the mandibles. At the distal end of this 

 narrow portion of the labium two rather long and stiff seta; are inserted, and along the sides 

 there is a row of such, which are shorter, less stiff, and at the same time slant forwards and 

 a very little upwards. In Oxopoei the mandibles are Hruily joined together approximately from 

 their base almost to their distal ends, leaving absolutely no room for a labium sternale ; but 

 the cephalic portion of the sternum projects between the bases of the mandibles in the shape 

 of a short triangle, on the dorsal side of which near the anterior end several setae are inserted 

 so high up that their place of insertion cannot be seen from the outside ; they are hidden 

 in the groove which marks the boundary between the mandibles. Three of them are of 

 considerable length, the longest of these reaching as far as the anterior end of the groove 

 in which they lie, that is to say, farther forward than even the apical labial setae in 

 Phrynoidae. In Tartarides the structure is the same as in Oxopoei, except that the number 

 of very long labial setae, at least in the species known to us, is restricted to two. In 

 Ricinulei — at any rate in Cryptostevima crassipalpe, the only species of which we have been 

 enabled to dissect a specimen, and without dissection the labial setae are very difficult to 

 discover — the sternum does not project between the bases of the mandibles, but nevertheless 

 three long setae are present also here, placed on the dorsal side of the sternum near its 

 anterior margin and hidden in the groove along the line of junction of the mandibles ; they 

 reach forward almost as far as the mandibles. We have pictured these setae in fig. 1 c on 

 PI. VII., but must add that this figure so far does not represent the natural condition in 

 that we have drawn the setae {I) as divergent, whereas in reality they lie so close together 

 that they seem to be but one. We are ignorant of the function of these labial setae in 

 Uropygi and Ricinulei, but we cannot but think that the agreement between the two 

 divisions in this respect indicates a certain degree of kinship. 



We hope that our figs. 1 c and 1 m will convey to the reader a clear idea of the mutual 

 position of the antennas and the parts of the mouth, when it is borne in mind that in fig. 1 c 

 the antennae have been removed from their place in the front (or upper) portion of tlie now 

 empt}' space, and that in the po.sterior portion of the same space the mandibles have similarly 

 been removed ; in fig. 1 m the antennae have likewise been removed from their place close up 

 t(5 the concave trough-like surface of the mandibles. 



In concluding this chapter we are tempted to say, that from a scientific point of view 

 it is rather fortunate that the group of Ricinulei was so little known down to the last 

 decennium of the 19th century, and particularly during the time when zoologists generally 

 were fully convinced that the Arachnida were nearly allied to Insects — an opinion which 

 perhaps is not yet quite abandoned, but which has been productive of much confusion in 

 the view taken of Arachnida generally. It is extremely probable that, if the Ricinulei had 

 then already been more known, the superficial similarity which exists between the cephalic 

 end of the body with the mouth in that order, and the corresponding parts in Insects, would 

 have served to confirm the opinions ruling during the period in question. In very many, perhaps 



' See Kraepelin, figs. 1 — 3. Kraepelin describes the labium sternale under the curious name of " Sternalstachel " or 

 sternal spine. 



s. 17 



