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Nemat. cursor or Nemat. ensiferus, that one is inclined to regard them as identical or at most as 

 varieties and this has indeed already been done by several authors. I may, however, be allowed 

 to remark, that these questions of synonymy can only then be solved with absolute certainty, 

 when specimens of these related indopacific species should be scrupulously compared with 

 specimens from the Antilles or from the east coast of the United States. Our knowledge of the 

 species of this genus leaves namely still very much to be desired: slight differences may after 

 all exist, which hitherto have been overlooked, but which nevertheless may be of specific or 

 vanetal value. So e.g. when studying some specimens from the Kei-islands referred to Nemat. 

 gracilis, I discovered a remarkable character of the dactyli of the 3 rd and 4 th pair of legs, by 

 which this species may easily be distinguished from the closely allied Nemat. undulatipés Bate. 



In the Caribbean Sea only one species has hitherto been observed, Nemat. cursor A. 

 M.-Edw., but this species is here very common, for during the winter cruise of the "Albatross" 

 in 1884 no less than 6810 specimens were taken in the eastern part of this sea (S. I. Smith, 

 in: Report on the Decapod Crustacea of the Albatross Dredgings off the East coast of the 

 United States during the summer and autumn of 1884. Wash. 1S86, p. 61): this number would 

 have been sufficiënt for supplying all the musea of the world with lots of specimens of this 

 species! Nemat. cursor occurs also off the East coast of the United States as far as 38° N. 

 Lat., and it is recorded from the Arabian Sea, the Gulf of Manar and the Bay of Bengal by 

 Professor Alcock, who has perhaps been in the occasion of comparing his species with specimens 

 from the West Indies. When this, however, has not been the case, I should be inclined to refer 

 his indian specimens to Nemat. undu/atipes Bate. Nemat. ensifcr (S. I. Smith) is found off the 

 eastern coast of the United States and also on the west coast of America from the Gulf of 

 California to the Galapagos Islands and Ecuador : both on the eastern and on the western 

 coast this species varies, however, considerably, so that on the western coast a more southern 

 typical and a northern different form have been distinguished by Faxon in his valuable and 

 beautiful work on the Stalk-eyed Crustacea, collected by the "Albatross". The typical Nemat. 

 ensiferus has also been recorded from the Hawaiian Islands and Sagami-bay, Japan, but the 

 species living in these localities will probably prove to belong to the variety producta Bate or 

 ientiipes Bate. The indopacific representatives of Nemat. ensifertis belong namely probably to 

 one or two distinct varieties producta Bate and tenttipes Bate, of which the former has been 

 observed near Yokohama, Japan, in the Indian Archipelago and off the New Hebrides, while 

 the variety tcnuipes is known also from Japan, from the Admiralty Islands, from the Bay of 

 Bengal and the Arabian Sea: these two varieties, however, are perhaps identical. The Eastern 

 Atlantic is likewise inhabited by a variety exilis Bate of this so extremely variable form : this 

 variety ranges from the South and South-west of Iceland, along the west coast of Ireland, to 

 the Canary Islands and has even been observed off the island of Ascension, it occurs moreover 

 both in the eastern and in the western Mediterranean. Nemat. gracilipcs A. M.-Edw. of a 

 splendid rosé colour and with wonderfully attenuated feet, was taken by the "Talisman" in 

 July 1883 in the deep waters of the Cape Verde Archipelago: no less than 500 specimens 

 of this species were then captured. 



While only three species are found in the Atlantic, a larger number occur in other 



SIBOGA-EXPEDITIE XXXIX a 3 . IO 



