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



Length. — The specimen, in the position figured, measured, from the front of the 

 head to the back of the third pleon-segment, less than one-fifth of an inch. A second 

 specimen, with numerous eggs, was slightly smaller. 



Locality. — Station 142, ofi" Cape Agulhas, December 18, 1873; lat. 35° 4' S., 

 long. 18° 37' E.; surface temperature, 65°"5. Two specimens, both females. 



Remarks. — The specific name refers to the capture of the specimens while adhering to 

 the screw of the vessel. 



Almost every part of the animal Showed a number of little packets of cells, crystalline 

 in appearance, embedded in brown matter, which I suppose to be pigment-cells ; it is to 

 these that figure p refers. The general efi'ect produced was a series of transverse, some- 

 what broken, lines of colouring, increasing in breadth towards the lower margins of the 

 large side-plates. 



Genus Metopa, Boeck, 1870. 



1842. Leucothoe, Kr0yer, Natnrhist. Tidsskr., E. i. Bd. iv. p. 157. 

 1845. „ Kr0yer, Naturhist. Tidsskr., E. ii. Bd. i. p. 539. 



1846 1 „ Krpyer, Voy. en Soand., pi. xxii. 



1850. „ Liljeborg, Ofversigt af Kongl. Vet.-Akad. Forhandl., Arg. 7. 



1851. ,, Liljeborg, Ofversigt af Kongl. Vet.-Akad. Forhandl., Arg. 8. 



1857. Montagua, Spence Bate, Synopsis; Ann. and Mag. Nat. Hist., ser. 2, vol. xix. p. 137 (5). 

 1857. „ "White, Popular Hist. Brit. Crust., p. 166. 



1859. Leucothoe, Bruzelius, Skand. Amph. Gamm., p. 96. 



1861. Montagua, Bate and Westwood, Brit. Sess. Crust., i. p. 53. 



1862. „ Spence Bate, Brit. Mus. Catal. Anipb., p. 54, p. 370. 

 1865. ,, Goes, Crust. Ampb. Maris Spetsb., p. 6. 



1868. „ Bate and Westwood, Brit. Sess. Crust., ii. p. 499. 



1869. Proholium, Norman, Last Eeport on Dredging among the Shetland Isles, p. 273. 



1870. Metopa, Boeck, Crust. Amph. bor. et arct., \>. 60. 

 1876. „ Boeck, De skand. og arkt. Ampb., p. 451. 

 1876. ,, Sars, Prodromus descr. Crust., p. 355. 



1884. ,, Scbneider, Crust, og Pycn. Kvaenangsfjorden, p. 71. 



1885. „ Sars, Den norske Nordbavs-Exp., p. 185. 



1886. Stenothoe, Gerstaecker, Bronn's Klassen und Ordnungen, Bd. v. Abtb. ii. p. 506. 



1886. Metopa, Norman, Mus. Norm., p. 14. 



1887. ,, Cbevreui, Crust. Ampb. Bret., p. 45. 



For the original definition, see Note on Boeck, 1870 (p. 400). Boeck only gives two 

 characters to distinguish this genus from Stenothoe. the three-jointed mandibular palp and 

 the one-jointed palp of the first maxillae ; of these the latter must be withdrawn, since 

 some species of the genus clearly have the palp of the first maxillae two-jointed. Boeck 

 apparently depends on Kr0yer for the description both of Leucothoe clypeata, Kr0yer, 

 which he makes the type of the genus Metopa, and of Leucothoe glacialis, Kr0yer, which 

 he calls Metopa glacialis. Though Kr0yer assigns a one-jointed palp to the first maxillae 



