EEPOET ON THE CRUSTACEA MACRURA. 379 



and robust, and fringed with hairs on the anterior margin, the third short and slender, 

 and fringed with hairs on the anterior margin, as are the two following joints, which 

 are subequal in length and terminally pointed. 



The first pair of pereiopoda is missing. The second and third pairs are long and 

 slender. The basal joints are short and robust, the second long and stouter than the first, 

 but not so long nor so stout as that of the second gnathopod ; the. three following joints 

 are subequal in length to and a little slighter than the previous joints, and are fringed 

 on each side with long and slender hairs. The fourth and fifth pairs of pereiopoda exist 

 as rudimentary buds. 



The pleopoda are so far developed as to resemble their permanent form. 



The first pair is long, slender, and single-branched, the terminal joint being fringed 

 with hairs. The second is shorter and biramose, as are also the three succeeding pairs, 

 each being a little shorter than the preceding, and all are fringed with hairs. The sixth 

 pair is long and well developed, more than twice as long as the telson and nearly as long- 

 as the sixth somite ; the outer branch is slightly longer than the inner and is armed 

 on the outer margin with a tooth, about midway between the base and the apex, and 

 beyond this fringed with long hairs, as well as on the inner margin, as are also the 

 margins of the inner branch. 



Length, 5 mm. (0"2 in.). 



Habitat. — The North Atlantic Ocean. 



MaMigopus spiniventralis, n. sp. (PL LXVII. fig. 4). 



Carapace about one-third the length of the body of the animal, anteriorly produced to 

 a long, sharp, straight rostrum, that is more than one-third the length of the carapace, 

 nearly as long as the ophthalmopod, and armed on the dorsal surface at the base with 

 a small tooth ; a still smaller one exists on the median dorsal line of the posterior 

 margin. 



The pleon has the first five somites subequal in length. The first has the dorsal 

 surface smooth, the second is armed with a small tooth ou the posterior margin, the 

 third, fourth, and fifth are similarly armed, but with larger teeth at right angles to the 

 surface. The sixth somite is longer than the two preceding somites together, and 

 is armed at the posterior margin of the dorsal surface with a small tooth directed hori- 

 zontally backwards ; it is also produced to a point at the postero-lateral angle, whereas 

 those of the five preceding somites are smoothly rounded off. From the ventral median 

 line of each somite except the sixth there projects a long tooth, broad at the base and 

 sharply pointed. The anterior teeth are curved forwards, but the direction is gradually 

 changed so that the posterior tooth is directed obliquely backwards. 



The telson is stout, terminating in a short fork (4z). 



