NO. 4 SCHULTZ: ISOPODA 7 



DESMOSOMIDAE 



The definition of this family by Menzies (1962b) should be modi- 

 fied slightly to include species in which the last three peraeonal segments 

 have coxal plates visible in the dorsal viewr. 



Desmosoma G. O. Sars 

 Desmosoma symmetrica, n. sp. 



(Plate 2) 



Diagnosis: Eyeless, pigmentless. Antennal bases deeply set into the 

 cephalon. Anterior edge of cephalon very slightly convex. Third per- 

 aeonal segment widest, general body outline gradually tapering towards 

 anterior and posterior ends. Coxal plates visible and acutely pointed on 

 anterolateral edges of first four peraeonal segments. Coxal plates visi- 

 ble on posterolateral edges of last three peraeonal segments. Peraeonal 

 segment five about as long as wide. Pleotelson of single segment with 

 large posterolateral teeth; posterior edge obtusely pointed. Peraeopods, 

 except first, furnished with plumose setae. First peraeopod with stout 

 setae; not modified for swimming; and with one large carpal seta ex- 

 tending half length of propodus. Antenna one with three flagellar ar- 

 ticles; antenna two with 12 or 13 articles. Maxilliped with three cou- 

 pling hooks; triarticulate palp with last segment small and tipped with 

 setae; molar process replaced by tuft of setae. Uropods biramous; exo- 

 pod very small, endopod with plumose setae. 



Measurement: Holotype female with marsupium 3.2 mm long. 



Type locality: 6836(1) ; Tanner Canyon; 469 m; Jan. 29, 1960; 

 green mud with shale fragments. Lat. 32° 36' 00"N, Long. 119° 05' 

 18"W. 



Distribution: Known only from type locality. 



Affinities: The new species is similar to Desmosoma gracilipes Han- 

 sen (1916), but diiifers from it in that the coxal plates of peraeonal seg- 

 ments five to seven are visible and the uropods are biramous. It is also 

 similar to D. tenuimana Sars (1899), but D. tenuimana lacks postero- 

 lateral spines on the pleon and does not have the coxal plates visible on 

 peraeonal segments five to seven. 



