250 U.S. NATIONAL MUSEUM BULLETIN 23 6 



Leg 4. External margin of basis near insertion of exopodite pro- 

 duced into spine (fig. 99e). 



Leg 5 of very characteristic appearance which can best be judged 

 from figure 99/ Coxae and basis of left and right sides fused, exopo- 

 dites and endopodites 1-segmented. Exopodites longer than endop- 

 odites, with external spinuous tubercle and apically produced into 

 externally directed, blunt tooth. 



Remarks. — This is undoubtedly a male specimen of Metis holo- 

 thuriae; the 1st segment of the endopodite may have become obscured 

 by the large, fleshy basis of leg 1 in my preparation. The shape of 

 leg 5 agrees particularly well with Nicholls' drawing (1941, fig. 4) 

 of this appendage in the adult stage. There is a slight difference 

 between the setal formulae given by Gurney (1927), Nicholls (1941), 

 Lang (1948), and my specimen, on which the missing seta of the 

 2nd exopodal segment of leg 3 in my specimen is remarkable. This 

 seta may have been removed during dissection, but the observation 

 of the fine setae is obscured by the long hau-s on the endopodal and 

 exopodal segments. 



Sewell (1940) split this species into two forms, differentiated by 

 length and small structural differences (f. minor, 9 0.45 mm.; f. 

 major, 9 0.82 mm., cT" 0.68). In regard to the considerable differences 

 in lengths of specimens from various localities and the great structural 

 variabihty, I have not accepted Sewell's division and I have entered 

 both forms in the synonymy of the nominal species. 



The geographical distribution of this species has been discussed by 

 Lang (1948, p. 778); it is knoAvn from the greater part of the northern 

 and southern temperate, subtropical, and tropical Atlantic and appears 

 to be well distributed throughout the tropical and subtropical Indo- 

 Pacific area. The following Pacific localities have become known 

 since the publication of Lang's monograph: Camorta Island and 

 Nancowry Harbour in the Nicobar Islands, and Addu Atoll in the 

 Maldive Archipelago (Sewell, 1940: measurements given above); 

 Dongara, Port Denison, and Rottnest Island in Western Austraha 

 (Nicholls, 1941a, 1942a, 1945: 9 up to 0.84 mm., cf up to 0.825 mm.); 

 and SeUick Reef in Southern Australia (Nicholls, 1941). The species, 

 or at least the developmental stages, preferably live on algae; isolated 

 specimens also have been recorded from plankton hauls, from sandy 

 and muddy bottoms, from holothurians, etc. The present specimen 

 was obtained from a sand sample taken some 340 feet from the reef 

 margin at Falarik in the Ifaluk Atoll. 



