ACANTHEPHYRA CURTIROSTRIS. 165 
extremity of the third, fourth, fifth, and sixth seoments ; the tooth on the 
third segment is the largest, those which follow decreasing in size succes- 
sively. The telson is equal in length to the fifth and sixth abdominal so- 
mites combined ; it is armed with ten submarginal spines on each side. The 
eye is dark brown, not wider than its peduncle, its proximal margin entire, 
the ocellus wanting; the ocular peduncle is furnished with a long, blunt 
tubercle or papilla on the inner side close to the margin of the cornea. The 
external spines of both pairs of antenne are short and acute; the antennal 
scale is long, broad near the base, tapering distally to the small apical tooth. 
The external branch of the swimmeret is shorter than the telson, but con- 
siderably longer than the inner branch. 
Length of a male, 85 mm.; rostrum from tip to posterior dorsal tooth, 
8.5 mm.; carapace, including rostrum, 25 mm.; telson, 18.5 mm.; antennal 
scale, 14 mm. 
The above described form I have considered as typical, but the “ Alba- 
tross” specimens show that this species is subject to great variation. In a 
single specimen from Station 3431 (an ovigerous female) there is a marked 
swelling in the median line of the gastric region ; the rostrum is not so high 
at the base as in the typical form, and ends in a longer, tapering acumen; the 
upper margin of the rostrum is in a line with the dorsal line of the carapace 
and the carapace is rather longer in proportion to the abdomen. The form- 
ula for the rostral teeth is 3. This form I have catalogued as Var. a (Plate 
XLII, Fig. 3). 
Other specimens agree with the last in most regards, but lack the pro- 
tuberance on the gastric area. The rostrum reaches to the end of the 
antennular peduncle or a little further. The dental formula is variable : 
+, 5, $, and §. These specimens I have designated as Var. 8 (Plate XLIII., 
4). 
In others the rostrum is yet longer, with upturned acumen; the telson is 
equipped with twelve pairs of lateral spines; the rostral teeth vary in num- 
_ber within the limits shown in the following formule: $3, 2,§. This form 
may be called Var. y (Plate XLIII., Fig. 5). 
It will be seen on looking at the list of stations given below that the 
typical form has a more southern distribution than the varieties. 
The extremes of variation here exhibited appear very great, but they 
are connected by transition forms in such a way that I am led to treat 
them as of merely varietal importance. 
