REPORT ON THE CRUSTACEA MACRTJRA. 



641 



pleurobranekial plume attached to the somite that supports the second pair of gnathopoda, 

 - -hown in the annexed table : — 



Pleurobranchiae, 

 A rthrobranehis, 

 Podobranchia, 

 Mastigobranclme, 



Observations. — This genus is closely allied to Pandalus, but is distinguishable from it 

 by having the frontal crest and rostrum armed with fixed teeth instead of movable spines, 

 the flagella of the first pair of antenna? very long and slender, the stylocerite sharply 

 pointed instead of being rounded and disc-like, and the posterior extremity of the mastigo- 

 branchial plate of the second pair of siagnopoda rounded off, short and abrupt, instead 

 of being produced to a long lash as it is in Pandakts. It differs also in having a pair 

 of branchial plumes connected with the second pair of gnathopoda. From Pandalopsis 

 it differs in a less degree, and that is in the existence of teeth instead of spines on the 

 dorsal crest, and in the presence of small or rudimentary mastigobranchial appendages 

 attached to all the pereiopoda excepting the posterior pair, whereas in Pandalus they 

 are absent from the four posterior pairs. 



These three forms have been associated by authors in the single genus Pandalus, but 

 I think the variation in their external structure is sufficiently important to warrant their 

 separation into distinct genera. 



Plesiontka uniprodueta, n. sp. (PI. CXIII. fig. 1). 



Carapace smooth, carinated anteriorly in front of the cardiac region. Eostrum as 

 long as the carapace, dorsal surface at the base crested and armed with seven closely 

 crowded teeth in the male, and with five in the female ; upper margin of the rostrum 

 smooth to the apex, under margin armed with sharp anteriorly directed teeth, extending 

 from the base to the extremitv. 



Pleon smooth, laterally compressed. In the female the posterior margin of the third 

 somite is produced to a sharp point in the median fine ; in the male only a trace of this 

 feature exists. 



Telson not so long as the lateral plates of the rhipidura, laterally compressed, dorsally 

 fiat, armed on each side at the dorso-lateral angles with three small spines and two or 

 three terminal spine-like hairs. 



94 mm. (3 - 7 in.). 



Fff SI 



