504 BULLETIN 54, UNITED STATES NATIONAL MUSEUM. 



ANALYTICAL KEY TO THE SPECIES OF THE GENUS IONE. 



a. Lateral parts or pleural lamellae of the abdominal segments in female twice as 

 long as the uropoda. Basal article of legs with an elevated eminence the 

 margin of which is irregular. Abdominal segments in male completely fused. 



lone brevicauda Bonnier 



a'. Lateral parts or pleural lamellae of the abdominal segments in the female not 

 longer than the uropoda. Basal article of legs with two elevations or carime 

 the margins of which are regular. Abdominal segments in male less com- 

 pletely fused lone thompsoni Richardson 



IONE CORNUTA Spence Bate. 



lone cornuta SPENCE BATE, Proc. Zool. Soc. London, 1864, p. 668; Lord's Natu- 

 ralist in British Columbia, II, 1866, p. 282. BATE and WESTWOOD, British 

 Sessile-eyed Crustacea, II, 1868, p. 253. GIARD and BONNIER, Travaux de 

 1'Institute Zool. de Lille et du Laboratoire Maritime de Wimereux, V, 1887, 

 p. 77. RICHARDSON, Proc. U. S. Nat. Mus., XXI, 1899, p. 869; Ann. Mag. 

 Nat. Hist. (7), IV, 1899, p. 338; American Naturalist, XXXIV, 1900, p. 

 308. BONNIER, Trav. de la Station Zool. de Wimereux, VIII, 1900, pp. 245- 

 247. RICHARDSON, Proc. U. S. Nat. Mus., XXVII, 1904, p. 75. 



Localities. Esquimault Harbor, British Columbia, on CaUianassa 

 longimana; Vancouver Island. 



"Mas: pleonem terminatum rotunde. 



"The male differs from the description of the European species 

 chiefly in having the caudal extremity terminating obtusel} r and in 

 having shorter antennae. 



"Fosrn., subequilateralis, lateralia cornua cephalonis habens recur- 

 vata, pleopoda longa et arborea. 



"The female has the antero-lateral horn-like process of the cephalon 

 curved posteriorly. The pereion is not quite equilate rally developed. 

 The coxae of the four anterior pairs of the pereiopoda are round, 

 and all attached to the antero-lateral margin of the segments of the 

 pereion. The coxae of the three posterior are the larger, and produced 

 posteriorly to a point. The pleopoda are long and fringed with arbo- 

 rescent branchiae. 



"This is the only species known besides that taken by Colonel 

 Montagu on the southern coast of England. 



"Length, male, i; female f of an inch. 



"Taken attached to the branchia of Callianassa longimana."- 

 SPENCE BATE.* 



"This species is much larger than that of the European form and 

 differs from it chiefly in having the lateral extremities of the somite or 

 segment which bears the antennae, posteriori}' produced up each side 

 of the head, after the manner of lateral horns. All the pereiopoda 



i lone cornuta Spence Bate is not included in the key because the description of 

 this form does not give details as to the characters, and because it is very probable 

 that the form described by Bonnier is identical with lone cornuta. 



*> Lord's Naturalist in British Columbia, ll, 1866, p. 282. 



