REPORT ON THE CRUSTACEA MACRURA. 269 



on the dorsal surface, the margins of which are produced on each side into a long, sharp 

 tooth, and at some distance there are two minute spines standing in a fringe of small hairs. 



The ophthalniopoda are tolerably large, and in the males reach nearly to the 

 extremity of the rostrum. They stand on a short stalk. 



The first pair of antennae, in the male, has the peduncle longer than the rostrum, in 

 some small specimens very much longer, a circumstance showing that the relative length 

 of these parts is not so important as is generally supposed. The prosartema is sharp 

 at the extremity, and the stylocerite is short and stunted, while the outer and anterior 

 angle of the first joint is produced to a sharp-pointed tooth. The third joint is 

 larger than the second, and cylindrical in form. The flagella of this pair are broken off 

 in all the specimens excepting one ; in this the outer branch is longer than the inner 

 and also than the peduncle, and the antennae are longer than the carapace. 



The scaphocerite is about the same length as the rostrum, except in a small 

 specimen where it is longer, but this appears to be due to the shortness of the rostrum 

 rather than to the length of the appendage. 



The pereiopoda are subequally robust, the third pair reaches as far as the extremity 

 of the rostrum. 



The pleopoda are of only generic value, except the posterior pair, which form the 

 lateral plates of the rhipidura ; the outer plate is channelled by a longitudinal groove that 

 strikes the outer margin at the line of the diaeresis and considerably within the distal 

 extremity of the plate. The inner plate is longitudinally grooved, much as in other 

 species. 



On the ventral surface of the pereion in the female the thelycum is very small, and 

 will be better understood by reference to the figure in the Plate (fig. 1'" ?) than from 

 any verbal description. 



The first pair of pleopoda carries a small and rudimentary appendage, which in the 

 male is developed into a large and longitudinally folded petasma (fig. l" $ ), the lateral 

 maroins of which are turned backwards and the median portion forwards, while the 

 extremity is furnished on each distal angle with an anteriorly-directed, sharp, slender 

 process or tooth. 



The second pair carries a double button-shaped tubercle at the base of the inner 

 branch. 



The branchiae (fig. 1, br) in their ultimate structure resemble those of the type of the 

 genus, and consist of a series of digital processes that divide into two branches and 

 generally terminate in four processes. 



The specimens referred to under Penseus rectacutus as having been taken off the Fiji 

 Islands, were taken associated with this species. They were placed under Pen&us 

 rectacutus because the thelycum corresponds wdth that species rather than with the type 

 of this. 



