THE ISOPOD CRUSTACEAN, ANCINUS DEPRESSUS(SAY). 



By Harriet Richardson, 



Collaborator, Department of Marine Invertebrates, United States National 



Museum. 



In 1818, Thomas Say" described the form which he referred to 

 the genus Na'sa, as N. depressa. A single dried specimen of this 

 species is to be found in the Academy of Natural Sciences in Phila- 

 delphia which I have had an opportunity to examine, and which I * 

 redescribed and figured in 1905. Another dried specimen of this 

 species is to be found in the British Museum, which, according to 

 Wliite^ and Hansen,** was presented to that museum by Thomas 

 Say.« 



In 1840, Milne Edwards f redescribed N. depressa, and instituted 

 for it the new genus Ancinus. The footnote given by Milne Edwards 

 for Ancinus depressus reads as follows : 



NoRsa depressa Leach, Collections du Musee brittaiiique de Londres. Cette 

 espece nous parait etre la meme que celle decrite sous ce nom par Say (Journal 

 of the Academy of Philadelphia, I, p. 483.) 



It is probable that Milne Edwards did not know^ that this speci- 

 men had been presented by Say, and therefore referred it to Leach. 



a Journ. Acad. Nat. Sci. Phila., I, 1818, pp. 483-484. 



6 Bull. U. S. Nat. Mus., No. 54, 1905, p. 272. 



c List of the Specimens of Crustacea in the Collection of the Bi'itish Museum, 

 1847, p. 105. 



* Quart. Journ. Micr. Sci., XLIX, 1905-6, new ser., p. 132. 



'^ Dr. Hansen says of this specimen : " Tlie specimen named seems to be the 

 only one existing in any zoological museum; at least I have asked for material 

 of this form in Paris and in American museums, but with negative results." 

 When I asked for Say's types at the Academy of Natural Sciences of Phila- 

 delphia I was told that they were not there, but on one occasion, when 

 I happened to be at the museum, I accidently discovered them. 



f Historie des Crustaces, III, 1840, pp. 225-226. 



Proceedings U.S. National Museum, Vol. XXXVI— No. 1663. 



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