NO. 4 SCHULTZ: ISOPODA 11 



NANNONISCIDAE 

 Nannonisconus, n. g. 



Diagnosis: Nannoniscidae with last peraeonal segment fused to 

 pleon. Pleon of single somite and at widest point wider than cephalon 

 or peraeon. Lateral outline of body concave. First antenna extending 

 only slightly anterior of cephalon, with bulbous organ attached to apical 

 article. The male first pleopods are different from all other Nannonisci- 

 dae in that they are not apically pointed and the proximal part is much 

 narrower than the medial or distal part. Uropods biramous. Nannonis- 

 conus is very much like Nannoniscus G. O. Sars, but the last two 

 peraeonal segments are fused in Nannoniscus, whereas the last 

 peraeonal segment and the pleotelson are fused in Nannonisconus. The 

 new genus also has a much broader pleotelson. The type species is N. 

 latipleonus. 



Nannonisconus latipleonus, n. sp. 

 (Plate 6) 



Diagnosis: Eyeless, pigmentless. Cephalon large with large antennal 

 bases. Anterior edge of cephalon with concave margin. Body outline 

 concave, narrowest part anterior part of longest peraeonal segment five. 

 Peraeonal segment one widest peraeonal segment. Posterior third of 

 pleotelson equals widest part of body. Margin of posterolateral edge 

 of pleotelson with large tooth ; posterior margin with large bilobed ex- 

 tension. All peraeopods similar to first. Antenna one with bulbous 

 apical segment and many plumose setae. Second antenna missing. Male 

 first pleopodal opercular lamella with enlarged posterior edge with 

 many marginal setae. Male second pleopod with large copulatory organ 

 with short posterior intrusive part. Maxillipedal endite with three cou- 

 pling hooks. Mandibular palp with three segments. Mandible with tuft 

 of setae replacing molar process. Uropods biramous; exopod shorter 

 than endopod, both with plumose setae. 



Measurements: Holotype male 2.8 mm long. 



Type locality: 2793(1) ; Redondo Canyon; 465 m; May 22, 1954; 

 blue-gray mud and large rocks. Lat. 33° 48' 00"N, Long. 118° 32' 

 00"W. 



Distribution: Known only from the type locality. 



Affinities: The species differs from other Nannoniscidae in that there 

 are spines on each of the anterolateral margins of the first four per- 

 aeonal segments. The most striking difference is that the pleotelson is 

 proportionately wider. The coxal plates of segments five to seven show 

 in the dorsal view. 



