6 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 121 



Leg 5 (fig. 28) with free segment elongated and slender, SG/x x 9/i, 

 with nearly parallel sides in dorsal view, and with 2 terminal setae 

 unequal, outer Slju and inner 19/x long. Few minute spinules on outer 

 distal surface of segment. No spinules near insertion of seta on body 

 near free segment. 



Leg 6 (fig. 29) a posterolateral flap on ventral surface of genital 

 segment bearing 2 naked setae 23^ and 25ju long. 



Spermatophore (fig. 30) inside body of male about 148iu x 68/i plus 

 neck of 14ju. 



Color in life resembling that of female. 



Etymology. — The specific name organicus, from Latin, relating 

 to musical instriunents, refers to the association of this species with 

 the organ-pipe coral Tubipora musica. 



Comparison with related species. — Among those species in the 

 large genus Lichomolgus, wherein the mandible has been described, 

 there are 3 that, like L. organicus, show a prominent toothlike 

 process on the proximal inner margin of this appendage. From these, 

 L. organicus may be readily distinguished. In L. actinophorus Humes 

 and Frost (1964) there is a single claw on the last segment of the 

 second antenna, the free segment of leg 5 in the female is somewhat 

 irregular and has a ratio of 2.1:1, the caudal ramus of the female has 

 a ratio of 3.5:1, and there is a setiferous sphere on the second segment 

 of the second maxUla. In L. decorus Humes and Frost (1964) there 

 is one claw and one clawlike spine on the last segment of the second 

 antenna, the last segment of the exopod of leg 4 has the formula 111,1,5, 

 and the free segment of leg 5 in the female is 2.2:1 with a basal ex- 

 pansion. In L. protulae Stock (1959) the shape of the body is trans- 

 formed, there are 3 strong claws and 2 setiform claws on the last 

 segment of the second antenna, the caudal ramus of the female has a 

 ratio of about 8.3:1, the free segment of leg 5 in the female is about 

 2.1:1, and the toothlike process on the mandible is directed distally 

 rather than proximally as in L. organicus. In addition, the females 

 of L. actinophorus and L. protulae are distinctly larger. 



There are 8 species of Lichomolgus in which the form of the mandible 

 is unknown. These may be separated from L. organicus, however, on 

 the basis of other characters (in each case using the female, except in 

 the last mentioned species where the female is unknown). In L. 

 dentipes Thompson and A. Scott (1903) the formula for the last 

 segment of the exopod of leg 4 is 111,1,5 and the free segment of leg 5 

 has a prominent toothlike inner process. In L. elegans Thompson and 

 A. Scott (1903) there is 1 claw on the second antenna and the body 

 is larger (1.5 mm) and more slender. In L. gigas Thompson and 

 A. Scott (1903) there is one claw on the second antenna and the body 

 is larger (2 mm) . In L. longipes (Sewell, 1 949) leg 5 is very long (about 



