NEMATOCARCINUS ENSIFER. 157 



This species has been previously known from off the eastern coast of the 

 United States (lat. 31° 41' N. to 41° 43' N., 588 to 2033 fathoms) through 

 the explorations of the " Blake " and the " Albatross." The Pacific speci- 

 mens, like those from the Atlantic side of the continent, vary considerably 

 in the length and trend of the rostrum, which may be either straight and 

 horizontal, or curved considerably upward. In some specimens, moreover, the 

 rostrum is armed on the lower margin with from one to three small teeth 

 which are wanting in the typical form, and this variation is almost invariably 

 accompanied by a difference in the abdominal segments. In the typical 

 form, without inferior rostral teeth, the dorsum of the third abdominal seg- 

 ment is prolonged into an acute tooth over the fourth segment, while the 

 succeeding segments are laterally compressed near the dorsum so strongly 

 as to present an almost carinated appearance. In the specimens with in- 

 ferior rostral teeth the third abdominal segment is prolonged backward over 

 the following segment in a less degree, and the prolongation is rounded off 

 behind instead of ending in a sharp point. The dorsum of the succeeding 

 abdominal segments, too, is rounder than in the typical form. The typical 

 form is the more southerly in its distribution, ranging (as far as the collec- 

 tion at hand determines) from 0° 36' S. to 7° 5' 30" N. (Stations 3363-3413), 

 while the other form is found between 16° 33' N. and 27° 34' N. (Stations 

 3418-3436). In rare cases, as in the specimens from Station 3415 (an inter- 

 mediate locality, be it observed), we find the rostrum of the typical form 

 combined with the abdomen of the more northern race. 



