REPORT ON THE AMPHIPODA. 1319 



"The mandibles are small, rounded, with a molar tubercle, but without palp. 



" The second pair of maxilla; consist of only one lamina. 



" The first and second pairs of perciopoda [First and Second Gnathopods] are 

 cheliform, the following [five pairs of Perwopods~\ ending with a claw-shaped 

 dactylus. 



"The uropoda are very thick, the second pair wanting, the inner rami coalesced 

 with the peduncles." 



In the species, however, which have come under my examination, the mandibles 

 are large as compared with the other mouth-organs, and by no means rounded, each 

 has a denticulate cutting edge, the left mandible a denticulate secondary plate, the 

 molar tubercle a long, straight edge set with cilia and minute spine-teeth. The 

 integument of the back appears to be remarkably homogeneous, not as generally in the 

 Gammarina much more flexible and less crustaceous at the folds between each segment, 

 hence I feel some hesitation in adopting as a character of the genus the statement that 

 the first two segments of the perason are as a rule distinct. The line of coalescence 

 between the two segments being in any case marked by a transverse ridge, a very 

 slight crumpling of the integument behind this ridge would give the same effect of 

 separation as that which in fact marks the division between the following segments. 



Cystisoma spinosum, $ (J. C. Fabricius) (PL CLIV.). Specimen A. 



1775. Oniscus spAnosus, Fabricius, Systema Entomologiae, p. 298. 

 1781. ,, „ Fabricius, Species Insectorum, t. i. p. 377. 



1787. ,, ,, Fabricius, Mantissa Insectorum, t. i. p. 241. 



1788. ,, „ Gmelin's Linnasi Systema Naturae, t. i. pars v. p. 3010. 

 1793. Cymofhoa spinosa, Fabricius, Entom. Syst., t. ii. p. 508. 



1842. Cystisoma Neptunus, Guerin-Meneville, Revue zoologique, juillet 1842, p. 214, pi. i. 



fig. 1. 

 1852. „ „ Dana, U.S. Explor. Exped., vol. xiii. pt. ii. p. 981, note. 



1862. Cystosoma Neptuni, Spence Bate, Brit. Mus. Catal. Ampb. Crust., p. 311, pi. 1. fig. 7. 



1873. Thaumops pellucida, v. Willemoes Subm, Proc. Roy. Soc. Lond., vol. xxi. p. 206. 



1874. „ „ v. Willemoes Subm, Pbil. Trans. Roy. Soc. Lond., vol. clxiii. 



pp. 629, 637, pis. xlix., 1. 



1874. Cystosoma neptuni, v. Willemoes Subm, Nature, vol. ix. p. 182. 



1875. Cystisoma Neptunus, v. Willemoes Subm, Trans. Linn. Soc. Lond., ser. 2, vol. i. pt. i. 



p. 24, pL xi. figs. 4-8. 



1876. „ „ v. Willemoes Subm, Proc. Roy. Soc. Lond., vol. xxiv. p. 570, 



1877. Cystosoma neptuni, Wyville Thomson, Tbe Atlantic, voL i. p. 129. 



1879. „ „ Pagenstecber, Sammlung gem. wissensch. Vortrage, ser. xiv. Hft. 315, 



316, p. 39. 

 1884. Thaumops pellucida, Kingsley, The Standard Natural History, vol. ii. fig. 99. 

 1884. Cystosoma neptuni, Kingsley, The Standard Natural History, vol. ii. fig. 101. 

 1886. Thaumatops Neptunus, Bovallius, Bihang till K. Svensk. Vetensk. Akad. Handl., Bd. 11, 



No. 9, p. 6. 



