104 THE VOYAGE OF H.M.S. CHALLENGER. 



similar size and structure; the fifth joint is more elongated and Blender, but similar in other 

 respects ; the distal joint forms a long claw, which is no thicker than the hairs which fringe 

 the margins of the preceding joints ; it is slightly swollen at its base and thru serrate. 



The two. following pairs of appendages are perfectly similar, save for the fact that the 

 basal joint becomes progressively longer; it is armed with a stout spine as in the 

 preceding limbs. 



The three distal thoracic appendages are in every case longer than the anterior pairs. 

 The elongation of the thoracic limbs and the stalked eyes give this species a certain super- 

 ficial resemblance to Munna. These appendages agree with each other and differ from the 

 anterior thoracic limbs in the great elongation of the proximal joint ; in the first two pairs 

 of these appendages the proximal joint has a stout spine about halfway along its length. 



The second joint is very much shorter, the third a trifle longer, the two together 

 nearly equalling in length the first joint ; the fourth and fifth joints are about equal 

 respectively to the second and third, they show at any rate the same proportions ; the 

 sixth joint is short and is armed with a single terminal claw ; the fourth and fifth joints 

 are armed along the inner margin with stout sharp spines. 



The uropoda are fringed along the inner margins, where they come into contact with 

 each other, with about four spines which are equidistant, but do not commence until 

 the latter half of the appendage. I did not observe any trace in these appendages of 

 the minute distal joints which occur in other species and represent the endopodite 

 and exopodite of the limb. 



Station 161, April 1, 1874, off entrance to Port Philip ; lat. 38° 22' 30" S., long. 

 144° 36' 30" E.; depth, 33 fathoms ; bottom, sand. 



Arcturus americanus, n. sp. (PL XXIII. figs. 5-8). 



A single Arcturus dredged to the east of the Strait of Magellan, and the only 

 species of the genus obtained by the Challenger from this locality, appears to be the type 

 of a new species. 



It presents certain resemblances to Arcturus co'p'pinrjcri of Miers, 1 from the same region, 

 but unless this form, like Arcturus baffini, has two varieties, one with dorsal spines and 

 one where they are absent, there can, to my mind, be no doubt as to their distinctness. 



The length of the single specimen, a female, is 21 mm. 



The body, as in Arcturus ccppingcri, is everywhere very densely covered with 

 tubercles, more so than in any other species described in the present Report. The 

 tubercles are, however, not so even as in the former species, a double row along the 

 back being prolonged into stout blunt spines. 



1 Account of the Geological Collection made during the survey of H.M.S. "Alert" in the Strait of Magellan and 

 on the coast of Patagonia, Crustacea, Froc. Zool. Soc. Lond., pt. i. p. 75. 



