510 



BULLETIN 54, UNITED STATES NATIONAL MUSEUM. 



Fig. 555.— Ion e 



THOiMPSONI. 



Maxilliped. 



Fig. 55(>. — lONE THoMPsoNi. First 



LAMELLA OF MARSUPIUM. X 10. 



hand. There tire two expansions or carina? on the basis of all the 

 legs, the anterior one being- only half as long- as the other. 



Male with all the segments of the thorax distinct. Eyes wanting. 

 Antenna^ conspicuous, six jointed. Anteunula?, three jointed. The 

 segments of the a])domen are more or less distinct, all six furnished 

 each with a pair of elongated leaf - 

 like tapering appendages. 



Two specimens were collected 

 by Mr. G. M. Gray at North Fal- 

 mouth, Massachusetts. They 

 were found on CalUamum, stimj)- 

 sonl. 



The species is named for Dr. 

 Millett T. Thompson, from whom the speci- 

 mens were received. 



7}/y>..— Cat. No. 21)091, II.S.N.M. 



This si)ecies is apparently very close to 7. cornutd Spence Bate, 

 from Vancouver Island. It agrees with Z connitit in the absence of 

 the elongated epimeral lobes (lames pleurales), in which both species 

 differ from /. tlioracioa (Montagu). Tone thompxoni and /. cornuta are 

 both much larger species than 1. thoracica. In the description of /. 

 cornuta," the author says that the coxa of the three posterior segments 

 of the thorax are larger than the four anterior, and are produced 

 posteriorly to a point. This is 

 not true of I. thoiiip>ioni^ in 

 which the epimera of the three 

 posterior thoracic segments are 

 smaller than those of the ante- 

 rior segments, although they 

 occupy the entire lateral mar- 

 gin, and the}' are rounded pos- 

 teriorly and not produced to a 

 point. Spence Bate also speaks, in reference to /. 

 eornut<(, of the antero-lateral "'horn-like process of 

 the cephalon* curving posteriorly.'' In /. thomp- 

 soni,, these lateral processes or lobes extend out 

 straight at the sides. Bate and Westwood, in describing I. corn uta, state 

 that the last pair of inner saccular branches of the pleopoda are almost 

 obsolete. There are but four pairs of inner branches in /, thompson!. 

 The al)ove quoted authors also describe the inner branches of the 

 pleopoda as gradually diminishing in size to the last pair, whereas 

 the outer branch(>s gradually increase in size. This is not true of 

 /, thotiip.soiil. 



Fig. 557.— Tone thompsoni. 

 Leg of sixth pair oi- 



ADULT FEMALE. X II5. 



Fig. 558.— Ione thomp- 

 soni. Male. ,<s. 



« Proc. Zool. Soc. London, 1864, p. 668. 



^ British Sessile-eyed Crustacea, II, 1868, p. 254. 



