Arcturidse in the U. S. National Museum. 



49 



the fourth segment there is but a single pair to a segment ; the lines are 

 not continued on the last segment, but are here replaced by a row of five 

 spines on the median line of this elongated segment. 



The second segment of the thorax is soldered to the head as in other 

 species, otherwise its dorsal armature is like that of the three following 

 segments. The epimera of the four anterior segments of the thorax are 

 moderately extended and bear from two to four spines ; between the 

 epimera and the lateral dorsal lines are two spines ; there is another spine 

 just behind the epimera. 



The three posterior thoracic segments are much shorter and narrower 

 than the preceding segments; the epimera bear but a single spine; the 

 spines of the lateral dorsal lines are smaller than the anterior spines of 

 the line; on the fifth segment, between the line and the epimera, are 

 three spines; on the sixth two spines, on the seventh one spine. The 

 first two segments of the abdomen are dorsally like the last segment of 

 the thorax ; the last segment is elongated and bears five rows of spines 

 one on the median line and two on each side ; there is a longitudinal row 

 of five spines on each valve of the operculum. Length of body 23 mm. 



Station 2807, off the Galapagos Islands, lat. 24' 00" S., long. 89 

 00' 00" W., 812 fathoms. One female with eggs (No. 21253, U. S. N. M.). 



Arcturus murdochi sp. nov. 



Arcti.iras hystrix Harger in Murdoch, Report Expedition to Point Barrow, 

 Alaska, p. 142, 1885. 



This species is closely related to A. hystrix, Sars, from off Flelgoland and 

 Lofoten, from depths ranging from 350 to 457 fathoms. 

 Both specimens of A. murdochi came from 13J fathoms 

 10 miles west of Point Franklin, Alaska, collected by 

 the Point Barrow Expedition. 



The head is deeply concave in front ; the sides of the 

 head extend forward in front of the eyes and end in 

 bifurcate projections. On the front margin of the 

 head is a single spine, conspicuous in being the only 

 spine occupying the median line throughout the length 

 of the animal. A spine on each side of the median 

 spine divides the space between the eyes, making a 

 row of three spines on the front of the head Justin ad 

 vance of the anterior line of the eyes. The median 

 spine is a little in advance of the other two. A row 

 of eight spines occupies the posterior part of the head ; 

 four of them are higher up than the eyes one pair 

 behind the eyes and one below on the margin of the 

 head ; the spines behind the eyes are the smallest. 



The antennulse are very short and small, hardly 



reaching the antepenultimate joints of the large an- FIG. 9. Arcturus mur- 

 tennse; the basal joints are wider and shorter than 

 those shown by Professor Sars in his figures of hystrix. 

 The basal joints of the antennae are small and are con cealed from a dorsal 

 view by the lateral projections of the head. 



11 BIOL. Soc. WASH., VOL. XII, 1898 



dochi. 

 (X 3 



