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



Thelitis oriental is, Rumph. 



Therms orientalis, Rumph, Mus., part 2, rig. d; Milne-Edwards, Hist. Nat. des Crust., t. ii. p. 286. 

 Cancer (Astacus) arctus, Hcrbst, t. xi. p. 80, pi. xxx. fig. 1. 



Scyllarus orientalis, Fabr., Suppl. p. 399; Latr., Hist. Nat. des Crust, t. vi. p. 181: Eneyel., 

 pi. cccxiv.; Desmarest, Consid. des Crust., p. 182, pi. xxxi. fig. 1. 



Habitat. — Station 188, Arafura Sea, south of New Guinea; September 10, 1874; 

 lat. 9° 59' S., long. 139° 42' E.; depth, 28 fathoms ; bottom, green mud. 



The only specimen taken was about 25 mm. (1 inch) in length, and had all the pleo- 

 poda in a very feeble and immature condition; just budding. From its young and 

 imperfect character I have not been able to determine the sex to which the animal 

 belongs. 



A fetus, Dana. 

 Scyllarus (part.), Fabr., de Haan, et Auct. 



This genus was established by Dana to contain several species that differed from the 

 typical Scyllarus in having the external antennae separated widely from each other, in 

 having no ecphysis attached to the second pair of gnathopoda, and in having nineteen 

 branchiae instead of twenty-one, as exist in Scyllarus. 



It corresponds with the fifth subgenus of De Haan's genus Scyllarus. 



Geographical Distribution. — This genus is found sparsely all over the northern 

 hemisphere, in the warm temperate regions. Arctus ursus is found on the European 

 shores as far north as the south coast of Devon and Cornwall, and south as far as the 

 Mediterranean. Arctus pygmseus and Arctus immaturus are from the Canary and Cape 

 Verde Islands, and Arcttis orientalis is from the Philippine Sea. Arctus americanus 

 has been found on the western coast of North America, Arctus vitiensis in the seas about 

 the Fiji Islands, and Arctus sordidus, and Arctus haani in the seas about Japan. There 

 is among the late General Hardwiek's drawings, in the possession of the Plymouth 

 Institution, the figure of a species resembling Arctus pygmseus, specifically named 

 leylonensis, after the locality where it was found, but I am not aware of its having been 

 described. 



Thenops scyllariformis, recorded by Bell 1 as having been found in the London clay, 

 exhibits scarcely a feature that is not common to Arctus. 



Arctus sordidus, Stimpson (PI. IX. fig. 3). 



Arctus sordidus, Stimpson, Proc. Acad. Nat. Sci. Phil., January 1860; Prodromus, &c, p. 8; 

 Crust. Macr. 



Carapace as long as wide at the anterior angles. ^Median crest bicuspidate ; anterior 

 cusp close behind the frontal margin; second much more elevated and larger than the 



1 Palceont. Soc. Trans., pi. vii. 



