Family ERYONIDAE. 



Of the Family Eryonidae seven species, one of which was new to science, have been 

 collected by the Siboga Expedition : they belong to the genera Stereomastis Sp. Bate and 

 Polycheles Heller. 



In a paper, published February 1912 in the "Records of the Indian Museum, Vol. VII, 

 Part I, N° 2", Messr. S. Kemp and R. B. S. Sewell, who had been able to compare two 

 specimens of Pol. typhlops Heller, captured by the "Talisman" off the Cape Verde Islands, 

 with Alcock's types of Pent. Hextii, did not only resolve on the specific identity of these two 

 species, but they came moreover to the important conclusion that the genera Polycheles Heller, 

 Pentacheles Sp. Bate and Stereomastis Sp. Bate ought to be united in one genus Polycheles 

 Heller. In his Report on the Stalk-eyed Crustacea, collected by the "Albatross", Mr. Faxon 

 had remarked in 1895 that "an examination of a large number of species discloses a gradual 

 transition in the development of the epipods, from large well developed organs through small, 

 delicate and thin ones, to merest rudiments in the shape of small expansions at the base of 

 the stem of the gill" and these words have evidently led Messr. Kemp and Sewell to their 

 conclusion, for in the Indian species such a gradual transition in the development of the 

 epipods does not occur, so that Professor Alcock in his "Descriptive Catalogue of Indian Deep- 

 Sea Crustacea" of 1901 has rightly recognized two distinct groups, to which he, however 

 erroneously, assigned the names of Polycheles and Pentacheles. 



In my opinion, however, the cited words of Faxon are, if well considered, not in con- 

 tradiction with Alcock's observations concerning the epipods and the signification, attached to 

 them by Kemp and Sewell, seems to me to be erroneous. After a careful examination of the 

 specimens collected by the Siboga expedition and after a careful study of the descriptions 

 of all the species which are at present known, I have been led to the conclusion that Alcock's 

 opinion is the only true one and that the two groups, distinguished by that author, must be 

 recognized and accepted. 



As has already been remarked, the epipods of Polycheles typhlops Heller = Pentacheles 

 Hextii Alcock are developed like in Alcock's genus Pentacheles, while Polycheles Alcock is 

 identical with Stereomastis Sp. Bate: it appears therefore necessary that the genus of which 

 P. typhlops is the representative, should henceforth bear the name of Polycheles Heller and 

 Stereomastis be the name of the other. 



S1BOGA-EXPEDITIE XXXIX a 2 . 1 



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