REPORT ON THE CRUSTACEA MACRURA. 63 



where Ibaccus v&rdi was obtained, it would without hesitation be pronounced to be an 

 undeveloped male of that species, which in most of its characteristics it much resembles. 

 It is about two inches and a half in length; and although a male, has seven strong 

 points or teeth on the distal margin of the anterior antennal plate, which iu Ibaccus 

 verdi is smooth in this sex, and has nine strong dental points in the female, the margin 

 also being more rounded than in the male, which is also the case in Ibaccus. brevipes, 

 and may be consequent upon its undeveloped state, since the males approach more 

 nearly to the general external characters of the female the younger they are. 



The pleopoda (PI. IX. fig. Iq) are apparently in a very immature condition, but they 

 exhibit features that appear not to belong to any other species. They are extremely 

 miuute, being indeed quite rudimentary. Upon being examined under a moderate magni- 

 fying power, they are seen to have two branches, the inner supporting a small secondary 

 lobe. Each branch, as well as the basal joint, is short, bulbous, free from hairs, and 

 attached at the base by a small pedicle. The branches are shorter than the basal joint, and 

 the inner carries a short, stout stylamblys. In most other details this species resembles 

 Ibaccus verdi, except that it is scarcely half as large. The Ki Islands, Arafura Sea, and 

 the Cape Verde Islands, whence the two forms have been obtained, are nearly antipodal 

 to each other, being in corresponding degrees of latitude north and south of the equator. 



Ibaccus alticrenatus, n. sp. (PL IX. fig. 2). 



Antebrachial or cervical notch deep and broad. Lateral margin of the branchial 

 region armed with eight teeth, of which the anterior is very large and the posterior rudi- 

 mentary ; none on the anterior angle of the carapace, which is produced to a point ; none 

 on the outer or lateral margin of the posterior plate of the second pair of antennas, and 

 five or six teeth of equal size, distantly separated from each other, on the distal margin 

 of the anterior plate. 



The pleon has the coxal plates converging laterally to a point more acute anteriorly 

 than posteriorly. Length, including antennas, 87 mm. (3 '5 inches). 



Habitat.— Station 167, west of New Zealand, June 24, 1874; lat. 39° 32' S., 

 long. 171° 48' E. ; depth, 150 fathoms; bottom, blue mud; two males, and two females 

 bearing ova. 



This species approximates in appearance somewhat to Thenus orientalis. It is widest 

 at the anterior margin of the carapace, and gradually narrows to the last somite of the 

 pleon. The antebrachial cleft is very deep and wide, and furnished on the posterior 

 margin with a fringe of rather long hairs. The anterior margin of the carapace is crenated 

 externally to the orbits, which are circular, rather large, open in front, and fringed round 

 the margin with a closely-packed blepharis. The outer and inner angles of the orbit are 



