214 Transactions of the Society. 



Male. Fig. 1. 



The shape, excluding the caudal projections, is roughly penta- 

 gonal, the rostrum, which is small, forming the apex, and the two 

 anterior sides being almost at right angles, so that the dorsal 

 surface, anterior to a transverse line drawn behind the insertions of 

 the second pair of legs, forms a right-angled isosceles triangle, 

 which occupies about a quarter of the length of the body. Behind 

 this is a sharp indentation, having the anterior side oblique, and 

 the posterior almost rectangular. Behind this indentation the 

 body attains its maximum breadth, and runs with parallel sides 

 until it reaches about half its length (not including the caudal pro- 

 jections) ; then there is another indentation, rather deeper than the 

 first. The body does not widen again posterior to this, but narrows 

 slightly and gradually to the hind margin, the lateral margin being 

 slightly undulating. The posterior margin fades, without any sign 

 of demarcation, into two great caudal projections, which are half as 

 long as the body, and the two, at their insertion, occupy the entire 

 width, so that the hind margin appears to be cleft with a deep tri- 

 angular notch. The outer edges of the caudal projections curve 

 inwards, and end in sharp, strong points; the inner edges, pos- 

 terior to the triangular notch, are nearly parallel to the long axis of 

 the body, but, at the point of junction of the triangle and straight 

 side, there is a longitudinal indentation, at the anterior end of which 

 is a strong, brown, chitinous spike, projecting backward and out- 

 ward, formed by the prolongation of the edge of the chitinous 

 notch ; and at the posterior end is a longer, thinner, white spike 

 projecting forward and inward. 



The whole notogaster is covered with a chitinous plate (not very 

 thick), which commences behind the epimera of the second pair of 

 legs, and coalesces with the caudal projections, which are wholly 

 chitinous. 



The first pair of legs are short (about three-eighths of the length 

 of the body), and are only separated from the rostrum by one of the 

 chitinous masses above spoken of. The coxa is short, the trochanter 

 large and powerful, the femur shortish and cyhndrical, the fourth 

 joint short and trapezoidal, the tarsus large, turned outward, and 

 having a strong spike from its posterior outward angle, turned 

 backward and outward. The sucker on this, and all the other legs, 

 is very large and complex. (Fig. 4.) 



The second pair of legs constitutes, as above stated, the leading 

 feature of the species, being different on the two sides ; that on the 

 right side attains the same distance beyond the rostrum as the leg 

 of the first pair, from which it only differs in the trochanter being 

 longer and thinner, and the tarsus being without the spike. The 

 leg on the left side is more than half as long again as that on the 



