REPORT ON THE CRUSTACEA MACRURA. 603 



Second pair of antennae long, slender, and furnished with a long, narrow and pointed 

 scaphocerite. 



Mandible having the molar process cylindrical, without a psalistoma, but furnished 

 with a slender three-jointed synaphipod. 



Second pair of gnathopoda very long, straight, projecting beyond the rostrum, four- 

 jointed, the coxa carrying a short, almost rudimentary, mastigobranchia. 



First pair of pereiopoda chelate, robust; carpos long, and articulating with the propodos 

 in the middle. Second pair long and slender, minutely chelate ; carpos long and multiarti- 

 culate. Posterior three pairs of pereiopoda simple, unguiculate, and fringed with spinules. 



Pleopoda biramose, foliaceous ; terminal pair having the outer ramus furnished with 

 a diasresis. 



The branchial arrangement corresponds closely with that of Merhippolyte agulhas- 

 cnsis, but there is an additional plume, as seen in the following table : — 



Pleurobranchiae, 

 Arthrobrancbias, 

 Podobranchise, 

 Mastigobranchiae, 



Geographical Distribution. — Southern area of the Atlantic and Indian Oceans. 



Observations. — This genus may easily be recognised by such external features as the 

 great length of the second pair of gnathopoda, and the small movable spine attached to 

 the postero-inferior margin of the sixth somite of the pleon. From the appearance of 

 Milne-Edwards' figure (he. cit., pi. xxv. fig. 8) I am inclined to believe that Hippolyte 

 marmoratus of Olivier, Lamarck, and Milne-Edwards, and perhaps also Hippolyte 

 aculeatus of Fabricius and Sabine, may belong to this genus. 



Nauticaris marionis, n. sp. (PI. CVIIL). 



Carapace dorsally crested, laterally smooth, having no supraorbital, antennal, or 

 hepatic tooth ; produced to a strong laterally compressed rostrum, which is anteriorly 

 deep, armed on the upper margin with from eight to twelve teeth, the posterior three of 

 which stand upon the frontal crest posterior to the orbital notch, and with three upon 

 the lower margin. 



The ophthalmopoda are pyriform. 



The first pair of pereiopoda is robust, the second pair slender and longer than the 

 first, the carpos being long and numerously articulate. 



The pleon is dorsally smooth and unarmed. Fifth somite short, and armed at its 

 postero-inferior angle with a sharp pointed movable spine. 



Telson tapering. 



