REPORT ON THE CRUSTACEA MACRUEA. IC", 



latero-frontal margins are smooth except for a fringe of hairs similar to those that cover 

 the carapace. Posterior to the cervical fossa are from eighteen to twenty-three teeth. 

 The number of the marginal teeth in our specimens is not constant on both sides, hi 

 some there are twenty-one on one side and twenty-three on the other, but since there 

 is more than one hiatus on the side with the less number, the greater is probably normal. 



The pleon gradually narrows dorsally from the posterior margin of the carapace to 

 the extremity of the telson ; the central ridge is carinated, and each somite is armed with 

 a well-formed and prominent tooth, the apex of which is at the anterior extremity of the 

 posterior half of each somite, and is produced to a sharp point and directed forwards. 

 The first somite is shorter and narrower than the others, and its coxal plate is reduced 

 to a solid protuberance that is hollowed in the anterior margin to receive the peltecleis of 

 the carapace, which, instead of projecting over the anterior margin of the first somite of 

 the pleon, as in Polycheles, falls into a hollow, and so forms an articulating joint 

 between it and the posterior margin of the carapace, as shown on PL XX. fig. 1. The 

 articulation of all the succeeding somites with one another takes place by a tubercular 

 process, which projects forwards from the anterior margin of each somite and fits into 

 a depression in the posterior margin of the preceding. The articulation of the first somite 

 with the carapace is well covered and protected by a thick brush of fine, short hairs; a 

 row of similar hairs, but less densely placed, fringes the posterior edge of the carapace, 

 and that of all the somites of the pleon. There is no orbital notch, but there is a slight 

 emargination in the anterior margin of the carapace, and the ophthalmopoda, which are 

 small and almost rudimentary, are not lodged in it as in Polycheles and Pentacheles, nor are 

 they laterally produced and covered by the projecting antero-lateral angle of the carapace ; 

 they are armed on the anterior surface as showm at Pis. XIX. c, c", c"" a, and XX. c, a, 

 with a small cusp or tooth, and lodged in the metope, above the antennae PL XX. c, a. 



The first pair of antennas (PL XIX. b) has the first joint of the peduncle expanded on 

 the inner side into a thin plate which is driven upwards by the pressure of the correspond- 

 ing expansion on the opposite side into a crest, the margin of which is serrate with thin, 

 spine-like teeth, and rounded off anteriorly ; the outer portion is thick and distended, 

 containing an internal auditory apparatus, which consists of a rounded calcified chamber 

 (o.c), flattened on the anterior and posterior surfaces, and connected with the walls 

 by a calcified channel, that opens by a long, narrow, slit-like foramen, just behind 

 the upper and anterior margin of this first joint, the surface of which is smooth and free 

 from any tooth-like processes such as exist in all the species belonging to Polycheles and 

 Pentacheles; the second and third joiuts are subcylindrical ; the third is shorter than the 

 second, and supports two flagella, of which the inner is tolerably robust, and about as 

 long as the carapace ; the outer is small and slender, being scarcely longer than the 

 peduncle of the antennas on which it stands. 



The second pah- of antennas (c) carries a long, projecting phymacerite (o, t) that curves 



