ISOPODS OF NORTH AMERICA. 63 



ANALYTICAL KEY TO THE GENERA OF THE FAMILY ANTHURID^. 



a. Labium terminating in two rounded lobes. Mandibles with cutting edge com- 

 posed of two or three blunt teeth. First maxillae simple, terminating in con- 

 spicuous and well-developed teeth. Maxillipeds with palp composed of one to 

 four articles. 



b. First five segments of abdomen coalesced into a single segment in the female. 

 Maxillipeds with palp composed of two articles. Flagella of both pairs of 

 antennae rudimentary in both sexes. Flagellum of first pair not greatly devel- 

 oped in male Genus Cyathura Norman and Stebbing 



b'. Segments of abdomen distinct in the female. 



c. Maxillipeds with the palp composed of a single article. Flagella of both pairs 

 of antennae in the female composed of only a few articles. In the male the 

 first pair has a multi-articulate flagellum. Mandible with a one-jointed 



palp Genus Ptilanthura Harger 



cf. Maxillipeds with a palp composed of four articles. Flagella of both pairs 

 of antennae multi-articulate; that of first pair in the male developed into a 

 remarkable brush-like organ. Mandible with a three-jointed palp. 



Genus Anthelura Norman and Stebbing 



a'. Labium terminating in two points, acuminate. Mandibles without teeth, ter- 

 minating in an acutely pointed lancet-like organ. First maxillae simple, spear- 

 like, terminal part armed with recurved teeth. Maxillipeds with basal part 

 narrow, oblong; palp composed of three articles. Segments of abdomen dis- 

 tinct in female. 

 b. All seven pairs of legs present in adult. Seventh thoracic segment normal, 



well developed. 

 c. Both pairs of antennae in both sexes with multi-articulate flagella. 



Genus CaJathura Norman and Stebbing 



c f . First pair of antennae in both sexes have the flagellum multi-articulate. 

 Second pair of antennae in both sexes have a rudimentary flagellum com- 

 posed of a single article Genus Paranthura Bate and Westwood 



b / . Seventh pair of legs absent in adult. Seventh thoracic segment very short, 

 abruptly narrower than preceding sixth segment and not as wide as the 

 abdominal segments. First pair of antennae composed of four articles, the 

 last article being the rudimentary flagellum. Second pair of antennae com- 

 posed of five articles Genus Colanthura Richardson 



13. Genus CYATHURA Norman and Stebbing. & 



First five segments of abdomen coalesced into a single segment in 

 the female. Flagella of both pairs of antennae rudimentary. Maxilli- 

 peds with a palp composed of two articles. Mouth parts otherwise as 

 in Ptilanthura and Anthelura. 



CYATHURA CARINATA (Krjziyer).c 



? Anthura gracilis DE KAY, Zool. New York, Crust, 1844, p. 44, pi. ix, fig. 34. 

 Anthura carinata KR0YER, Naturh. Tidsskr. (2), II, 1846-49, p. 402; Voy. en 

 Scand., 1849, pi. xxvii, fig. 3. 



"Norman and Stebbing' s key has been used with slight modifications. See Trans. 

 Zool. Soc. Lond., XII, 1886, Pt. 4, pp. 121-122. 



&See Norman and Stebbing, Trans. Zool. Soc., Lond., XII, 1886, Pt. 4, p. 121, for 

 characters of genus. 



c Norman and Stebbing give an excellent description of this form. 



