PYCNOGONIDA. 57 



Rhynchothorax atjstralis. 



(Plate VIII., fig. 3.) 

 Specific characters : — 



Body very robust, with lateral processes quite close together, and with median tubercles on 

 the segments. 



Chehfori absent. 



Palps 5-jointed, the second joint with a very strongly developed spur dorsally. 

 Ovigers 10-jointed, with a terminal claw, the last four joints with a couple of spines on an 

 enlarged base. 



Legs short, terminal claw with two small auxiliaries. 



Body very robust, with the lateral processes short and quite close together, widest 

 across the first lateral process, and about half the breadth across the last. 



The posterior articulation of the trunk is deficient, but immediately in front 

 of where it should be, as on the preceding segments, is a stout median tubercle, bluntly 

 pointed, and very slightly inclined forwards. 



The Cephalon is expanded, but very short. The Ocular tubercle, which is stout, 

 projects forwards and upwards over the base of the proboscis. It bears four well- 

 developed eyes, the posterior pair being a little the larger, and terminates above them 

 in a short cone. Measured from the anterior margin of the ocular tubercle, the 

 cephalon is half the length of the first segment of the trunk. 



The Abdomen is long, about as long as the two combined segments from which 

 it originates. 



Proboscis is stout, conical, a little longer than the first trunk segment. A 

 conspicuous slit marks the mouth as the animal lies in its normal position. 



Chelifori, no trace. 



Palps. These appendages only comprise five joints, and are very curiously 

 modified (fig. 3a). Each rises at the side of the proboscis and extends but little 

 beyond it. The first joint is short and stout, the second is the longest of the 

 appendage ; its dorsal extremity is prolonged forwards and upwards as a stout spur. 

 The third joint is about half as long as the shaft of the second, it is enlarged distally, 

 a stout dorsal tubercle bearing a tuft of setae ; a few other setae are more scattered. 

 The fourth joint is small and setose, while the fifth, which is also richly setose, is 

 reduced to a mere button. 



The Oviger is very slender, ten-jointed, and rises ventro-laterally at the neck 

 (fig. 3a). The first three joints are short, and progressively lengthen, but only to a 

 slight degree. The fourth is nearly as long as the three together. The fifth is 

 shorter, but swollen distally. The sixth is shorter still. No setae, are discernible on 

 any of these joints. Of the four terminals the first three are sub-equal in length, 

 but their dorsal surfaces become more and more curved. Ventrally, also, there are 

 prominent projections which bear the denticulate spines. The terminal joint is very 

 broad, and a little longer than the others ; its dorsal outline is very much curved, 

 and ventrally a large swelling occupies almost the whole surface ; one small spine is 



T 2 



