Ccphalotliorax in Eicinnlei 117 



of the cncullus. Sorensen (a, pp. oO.") — 507) has shown that the plate which projects above 

 the antennte and the parts of the mouth in Trogulus is in reality formed by the union of 

 two large flat projections of the eye tubercle, and — contraiy to the opinion of Karsch — we 

 believe these flat projections in Trogulus to be really the morphological equivalents of the 

 cncullus in Cryptostemina, because in two genera belonging to Troguloidtf, viz. Dicranolasma 

 and Amopauin, these plates are free anteriorlj', and carry each one eye. This proves decisively 

 that they belong to the first segment of the cephalothorax. How far this segment reaches 

 back on the cephalothorax in Troguloidas and Thelyphonoidee cannot be determined, whilst 

 it is free posteriori}' in Cryptostemmatoida?. 



The dorsal surface of the cephalothorax is marked by a varying number of grooves 

 of which only the two most important need be mentioned here. The first of these is a 

 longitudinal groove of somewhat varying length, in some cases terminating posteriorly in 

 a short and shallow transverse groove, which probably indicates the boundary between the 

 head and the thorax, such as doubtless is the case with the transversal impression on the 

 cephalothorax of most Aranese theraphosa? Sim. (Ar. tetrapneumones Latr.) and PhrynoidaB. 

 Secondly we have to mention a sometimes rather slight transverse groove (our " sulcus trans- 

 versus posterior ") which probably marks the boundary between the two thoracic segments, as 

 it terminates on either side of the cejihalothorax, opposite the space between the two hindmost 

 pairs of legs. Behind the last-mentioned groove the cephalothorax is rounded rather steeply 

 downwards to what looks like its posterior margin, but which in reality is only a projecting, 

 transverse, slightly downward-bent ridge, and constitutes a part of the mechanism for 

 coupling together the cejahalothorax and the abdomen. The lower surface of that produced 

 ridge is, in reality, the continuation of the dorsal surface of the cephalothorax, and the 

 real posterior margin of cephalothorax is found at the end of the lower surface mentioned, 

 and has the character of an extremely thin ridge bounded by a shallow groove. 



It should be added that the solitary pair of spiracles is placed on the cephalothorax, 

 not, as has been quite naturally sujjposed, on the abdomen. 



Sternum. — It is not visible from the outside between the coxse of the second, third, 

 and fourth pairs, because these latter all meet externally in the middle line of the body; 

 but it is plainly seen on the inside of the dermoskeleton. The central portion of the sternum 

 is a small somewhat oblong plate, situated behind the posterior margin of the second pair 

 of coxse and between those of the tliird pair ; when the fourth pair of coxae are removed 

 (PI. VII., fig. 1 c) this plate {st.) is seen to project behind the third pair. From the under 

 surface of this plate a narrow strip proceeds on either side along the posterior upper margin 

 of the third pair of coxee, to which it is firmly united, and near the lateral margin of the 

 cephalothorax it is seen to be continued in a triangular plate, inside the lateral border 

 of the cephalothorax, on wliich the spiracle on either side is placed. Anteriorly the plate 

 above-mentioned is continued between the coxse of the second pair, in the shape of a narrow 

 strip, widening a little at its anterior extremity, from which another narrow, transvei-se strip 

 proceeds along the upper margins, first of the second and beyond this, of the first pair 

 of coxae, as far as to the lateral border of the cephalothorax. In front of the anterior 

 margin of the second pair of coxas we notice an extremely small free projection from the 

 middle portion of the sternum, which lies a little lower than the strip along the anterior 

 margin of the coxae, and which on the dorsal side carries the labial setaj (PI. VII. , fig. 1 c, I), 

 which will be treated of more fully in the description of the mouth. 



