ACANTHEPHYEA CURTIROSTRIS. 165 



extremity of the third, fourth, fifth, and sixth segments ; 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 spinel 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 antenna) 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.; antenna! 

 scale, 14 nun. 



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 bas3 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 ^. This form I have catalogued as Var. a (Plate 

 XLIII., 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 : 

 ^, |, I, and |. These specimens I have designated as Var. 13 (Plate XLIII., 

 Fig. 4). 



In others the rostrum Is yet longer, with upturned acumen ; the lelson is 

 equipped with twelve pairs of lateral spines ; the rostral teeth vary in num- 

 ber within the limits sliown in the following fornuilo3 : |, |, |. This form 

 may be called Var. 7 (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. 



