Arcturidse in the U. S. National Museum. 



51 



FIG. 10. Afitacilla 

 diomedece. (XC.) 



The abdomen is constricted at the base and has sub- 

 parallel sides ; from the slight postero lateral protuber 

 ance it narrows rapidly to the apex. 



The animal is throughout smooth and glabrous ; the 

 median line is light in color; on the fourth segment 

 the light color broadens out and the sides are blotched 

 with dark shadings made up of small black spots ; all 

 the articles of the antennal peduncles have a narrow 

 ring of black at the distal ends, except the fifth. 



Described from a single female dredged by the 'Al 

 batross ' in the Straits of Magellan from a depth of 17 

 fathoms (Station 2774). The marsupium is filled with 

 eggs (No. 21251, U. S. N. M.). 



Astacilla caeca sp. nov. 



The head is deeply excavated to receive the anten- 

 nulse ; the excavation is deeper at the sides than on the 

 median line ; a rostriform point extends between the 

 antennulse. The lateral prolongations of the head have 

 two paired digital processes near the lower margin ; 



one pair only can be seen from above. The antennae 

 reach back to the end of the sixth segment. As in 

 other species of the genus, the first thoracic segment 

 is solidly united to the head ; the lower margins of the 

 segment are tubercular. The second thoracic segment 

 is short and narrow ; the third is a little longer and 

 wider ; the fourth or long segment is yet wider at the 

 anterior end, caused by the swellings at the insertions 

 of the legs ; after this it tapers gradually to near the 

 posterior end, where the taper is more rapid. The 

 fifth, sixth, and seventh segments are successively 

 narrower. The median line of the head and thorax 

 is tubercular; the head has one tubercle near the front 

 and another on the postcephalic lobe ; all thoracic seg 

 ments have a tubercle on the line ; the lateral mar 

 gins of all are angular ; above the epimeral projections 

 of the fifth segment are four paired tubercles. The 

 first segment of the abdomen is narrow and forms a 

 neck between the thorax and the broad and angular terminal segment. 

 The terminal segment has a pair of angular projections on each side of 

 the margin ; between the angles the margin is but little arcuate ; posterior 

 to the last angular projection the outline is that of an equilateral triangle. 

 Attached to the carapace are several specimens of Foraminifera which 

 Dr. Flint tells me belong to the genus Truncatnlina. 



Both specimens have been repeatedly examined for a trace of eyes with 

 out success. 



Length of the large specimen (female) 9 mm., measured from the front. 

 Station 2714, lat. 38 22' 00" N., long. 70 17' 30" W., 1825 fathoms 

 (No. 12026, U. S. N. M.). 



FIG. 11. Astacilla 

 cceca. (X 3.) 



