REPORT ON THE CRUSTACEA MACRURA. G13 



thickly fringed with short, stiff hairs, between which and the ecphysis stands a two-jointed 

 continuation. 



The first pair of gnathopoda (fig. 2h) corresponds both with that of Hippolyte and that 

 of Spirontocaris, and supports a small mastigobranchia and a rudimentary podobranchia. 



The second pair of gnathopoda is pediform, five-jointed, and robust ; it differs from 

 the same appendage in both Hippolyte and Spirontocaris is having no basecphysis, but 

 it supports a rudimentary mastigobranchia. 



The first pair of pereiopoda is short and robust, the carpos being long and distally 

 increasing in diameter, and produced anteriorly a short distance above the propodos ; the 

 propodos is long, slightly curved, and not broader than the distal extremity of the carpos ; 

 the pollex and dactylos are short. The coxa supports a rudimentary mastigobranchial 

 appendage. The second pair of pereiopoda is long, slender, and minutely chelate, having 

 the carpos seven-articulate ; the coxa carries a rudimentary mastigobranchial stump. 

 The third pair is long and simple ; it has the carpos long, cylindrical, and distally produced 

 above the propodos, which is also long and cylindrical and slightly spinulous on the 

 posterior margin ; the dactylos is short, robust and serrate. The coxa supports the stump 

 of a mastigobranchial appendage. The fourth and fifth pairs of pereiopoda resemble 

 the third in general structure, but do not carry even the radimentary stump of a 

 mastigobranchial appendage. 



The pleopoda are short, broad, biramose and foliaceous. 



The rhipidura is strong and well developed, but the telson in our unique specimen is 

 broken. 



Observations. — This species appears to be identical with Milne-Edwards' description 

 of Hippolyte gaimardii in all points, excepting that in our specimen the second pair of 

 gnathopoda reaches as far as the extremity of the scaphocerite, whereas in his description 

 it is described as being shorter. Milne-Edwards' specimens were obtained near Iceland. 

 It also corresponds very closely with Hippolyte rectirostris of Stimpson, 1 which was 

 taken in deep water off the Port of Hakodadi, at the northern extremity of Japan. 



Hetairus tenuis, n. sp. (PI. CIX. fig. 3). 



Rostrum about two-thirds the length of the carapace, narrow immediately in advance 

 of the frontal margin, and deepening slightly anteriorly, superiorly armed with six teeth 

 inferiorly with three. 



Ventral surface of each of the three posterior somites of the pereion armed with a 

 pair of teeth. 



Pleon smooth, third somite slightly gibbous and dorsally produced in the median 

 line. 



1 Proc. Acad. Nat. kjci. Philad., January 1860, p. 102. 



