RICHARDSON : ISOPODES DU SANDWICH DU SUD. 399 
Serolis laevis sp. nov. 
Four specimens of a new species of Serolis were obtained by M. 
Dr. Lahille in 1910 at the Sandwich du Sud. This species is close 
to Serolis plana Dana, to Serolis convexa Cunningham and to Se- 
rolis gaudichaudii Audouin and Milne Edwards. In comparing 
them with the three species mentioned, y will point out the 
points of resemblance and the points of difference. 
This species differs from Serolis plana as described and figu- 
red by Jana * (1) in not having the margins of all the thoracic 
segments «closely in contact, quite to the lateral margin», the 
outline being broken at the fifth segment, which is somewhat 
narrower than the fourth; (2) in having the flagellum of the se- 
cond antennae longer, extending to the middle of the third tho- 
racic segment instead of to the middle of the second segment; (3) 
in having the tip of the last abdominal segment truncate in three 
of the specimens and slightly upturned; (4) in the different shape 
of the eyes which are reniform; (5) in having the median and 
lateral ridges of the terminal abdominal segment almost obsolete, 
as well as the lateral tooth on either side; and (6) in the absence 
of the prominences of the fourth segment of the thorax, just 
within the epimeral sutures. These differences are constant in 
all the specimens. 
Beddard ? says of Serolis convexa Cunnigham ?, that 16 1s clo- 
sely allied to Serolis plana and that 1t is «Almost impossible sa- 
tisfactorily to separate them». The present species agrees with 
Serolis convexa in having the last two segments of the thorax 
narrower than the preceding ones; in the shape of the eyes and 
in the longer first and second antennae. It differs, however, in 
the absence of the «three well marked ridges, a median, inte- 
rrupted in the middle, and two lateral, each terminating in a 
sharp point». It also differs in the longer lateral angles of the 
sixth thoracic segment, which extend some distance beyond the 
lateral angles of the second and third abdominal segments, but 
in Serolis convexa are short, not extending beyond the angles of 
1 U.S. Expl. Exp., x1v, 1853, Crust., Pt. 2 pp. 794-795, pl. 53, figs. 1*-c. 
2 Challenger Report. The Isopoda, Pt. 1, 1881, p. 38. 
3 Trans Linn. Soc. London, xxv11, 1871, pp. 498-499, pl. Lix, fig. 3. 
