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Show 52 DR. H. J. HANSEN ON CRUSTACEANS [Jan. 20, 7. On the Crustaceans of the Genera Petalidium and Sergestes from the 4 Challenger/ with an Account of Luminous Organs in Serges tea challengeri, n. sp. By Dr. H. J. Hansen (Copenhagen). [Received November 29, 1902.] (Plates XI. & X I I .1) During a stay in London in July and August, 1902, I examined various groups of Crustacea in the British Museum (Natural History). I beg the Director, Professor E. Ray Lankester, and Mr. F. Jeffrey Bell to accept my sincere thanks for the free use of the collection and for their kind help. In the paper " On the Development and the Species of the Crustaceans of the Genus Sergestes" (Proc. Zool. Soc. Lond. 1896, pp. 936-70) I have given a revision of this extensive genus. I had studied a very rich material of pelagic forms belonging to the Copenhagen Museum, among which are all the types of Kroyer; besides I had examined types of 5 species established by Chun, Metzger, and Ortmann. Among other things, I proved that " of the 59 (or 60) hitherto described species only about 20, or one-third of the total number, have been established on adidt animals, such as have almost or entirely arrived at sexual maturity; and that almost all the other species are true larvce, and even of these a considerable number are larval stages of species already established on adult specimens, . . ." Of earlier authors, C. Spence Bate has produced a very large contribution on the genus Sergestes, extending to eighty-eight quarto pages and seventeen plates, in his " Report on the 4 Challenger ' Macrura." He established the genus Petalidium on a new species, described 24 new species of Sergestes &c. In 1896 I wrote (p. 939) : " This large contribution is of course of great importance, but unfortunately neither the descriptions nor the figures are so good as could be wished, and in numerous instances . . . a re-examination of the type specimens is absolutely necessary -the greater part of the new species are but larvae." I have now studied all types which are preserved in the British Museum, and the present paper contains the results of my examination. Bate describes 31 species of Sergestes as examined by himself : of these, 24 are established as new to science, 6 are considered to be Kroyerian species, and one is referred to S. atlanticus H. M.-Edw. The types of 9 of the species established by Bate do not exist in the British Museum; some specimens mentioned in his work and belonging to other species are also absent; but several specimens belonging to various species and omitted in the Report were found in the collection. I am therefore only able to give more or less incomplete notes, based on the study of the 1 For explanation of the Plates, see p. 78. |