202 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 117 



Acanthohaustorius intermedius, new species 



Figures Ic, 3e, 4a, 24, 25 



Material examined. — Barnstable Harbor, Mass., Beach Point, 

 coarse sand, low water, 12°C., May 19, 1962, E. L. Mills: 1 9, bolo- 

 type, 1 cf , allotype (NMC 7046); same locality: 6 99 (5 ov.), 3 cTcf, 

 paratypes (NMC 7047). Alhatross-\Ql, cruise 70, coll. 5, 40°51', 

 68°20', Digby bag, 25 fms., Dec. 7, 1955: 1 cf (NMC 7048). 

 Alhatross-\0\, sta. 86, 41°14', 67°28', Smith grab, 24 fms., Aug. 24, 

 1957: 2 99, 3 imm. (NMC 7049). U.S. Fish Comm. Fish Hawk sta. 

 1802, 1874: 10 adult specimens. Cape Cod Bay, Nobscussett Beach, 

 open sand near breakwater, low-water level, Sept. 9, 1963: 5 adult, 

 45 imm. (MBL, author collections). Alhatross-\0\ , sta. 63, 41°26', 

 68°19', Smith grab, Aug. 24, 1947: 2 99, ov.; Alhatross-lOl , sta. 70, 

 40°57', 67°52', Smith grab, Aug. 24, 1957: 2 adults; Vineyard Sound, 

 Middle Ground, from Blueback, April 5, 1962: 12 adults (USFW, 

 K. L. Wigley collection). 



Description. — Female, 4.5 mm. Head wider than long, outer 

 margins smoothly convex, rostrum broad and blunt, antennal sinus 

 moderately deep. Eyes apparently lacking. Body strongly arched. 

 Pleosome segments very broad; margin of pleon 3 produced mid- 

 dorsally as a large blunt-conical posterior process. 



Antenna 1 : peduncular segment 1 very short, deep, segment 2 

 subequal in length ; flagellmn of 5 slender segments, accessory fiagellum 

 equally 2-segmented. Antenna 3 peduncular segment 4 with short 

 posterior lobe; segment 5 tumid; flagellum 5-segmented, 2nd segment 

 smallest. Upper lip: apex smooth. Lower lip: inner lobes very 

 broad apically. Mandibular incisor simple, incisor unicuspate, 5 ac- 

 cessory blades; palp slender, comb row of 9 short spines, apex with 9 

 slender spines. Maxilla 1: inner plate small, with 7 marginal setae; 

 palp short, sparingly setose; accessory baler lobe shallow. Maxilla 2: 

 outer plate expanded, length about 1% times the inner plate, apex 

 blunt, inner margin distally with about 12 plumose setae. Maxilliped : 

 inner plate short, broad ; outer plate convex laterally; palp short and 

 broad, terminal segment stout, distal margin short. 



Gnathopod 1 : coxa rounded below, with 3 posterior plumose 

 setae; segment 2 linear; segment 5 moderately expanded, ventral 

 setae cleft tipped; segment 6 much shorter. Gnathopod 2: coxa 

 with 7 posterior setae ; segment 2 very slender ; segment 5 longer than 

 linear segment 6, with 3 groups of ventrodistal comb spines. 



Peraeopod 1: coxal plate semilunate, posterior margin with 8 

 plumose setae; segment 4 not expanded, weakly plumose; segment 5 

 shallow, posterior lobe with 10 circlet spines and 1 plumose seta; 

 segment 6 small, with 8 marginal spines. Peraeopod 2: coxal margin 

 strongly convex below, segment 4 little expanded, margins plumose; 



