238 A HISTOEY OF RECENT CEUSTACEA 



pair of trunk-legs are uniform in length, while in the 

 other five genera they are unequal. Ghtorotocus, however, 

 has the wrist of these legs two-jointed, while in Borodotes 

 it is six-jointed. The ' palp ' of the mandibles is two- 

 jointed in Ghlorotocus, undescribed in Borodotes, three- 

 jointed in the other five genera. 



Panddlus, Leach, 1814, has the 'anterior portion of 

 the carapace carinated and produced to a long rostrum 

 that is armed on the dorsal or upper surface with movable 

 spines, intermingled with hairs, and on the lower surface 

 with fixed and rigid teeth.' Also, the first pair of antenna 

 are not longer than the carapace, and the spine on the 

 outer margin of their basal joint is obtusely pointed. Two 

 British species belong to this genus, Panddlus Montagui, 

 Leach, which has priority over the more generally used 

 name, annulicornis, Leacb, and Pandahis brevirostris, 

 Katbke. There are numerous other species in various 

 parts of the world, among which Pandalus narwal, Milne- 

 Edwards, in the Mediterranean, exceeds a length of five 

 inches. Pandalus Montagui, though its usual length ia 

 given by Bell as from two to two and a half inches, is said 

 by S. I. Smith to attain a length between four and five 

 inches off the coast of the United States. 



Pandalojms, A. Milne-Edwards, 1888, is most ob- 

 viously distinguished from Pandalus by having the flagella 

 of the first antennae much longer than the carapace. The 

 other genera are distinguished by some minute and curious 

 characters, for while the frontal crest and rostrum of 

 Pandalus are armed on the upper surface with movable 

 spines only, in Nothncdris, Spence Bate, 1888, the dorsal 

 crest has several spines that articulate in sockets, and 

 several teeth that are fixed and rigid, but in Plesionika, 

 Spence Bate, 1888, and Heterocarpus, A. Milne-Edwards, 

 1881, there are teeth only, and no movable spines. In 

 Plesionika, as also in Nothocaris, the spine on the outer 

 margin of the basal joint of the first antennae is large and 

 pointed, but in Heterocarpus it is said by Spence Bate to 

 be rudimentary ; yet he identifies with the type species, 

 Eeteromrpus ensifer, A. Milne-Edwards, the Heterocarpus 



