86 Cumacea: 9. Leuconidae, 4. Pseudoleucon, 10. Diastyloididae, 1. Diastyloides 



tooth. Carapace with a transverse pair of denticles behind the eyelobe, and 

 a longitudinal couple a little further back. Pedigerous segments together 

 longer than carapace, 1^* short, 2'^'^ long, last four well separated, with short 

 setae on antero-lateral margins. Pleon ventrally with scattered plumose setae, 

 telsonic segment with setae dorsally on the hind margin. Antenna 1, 3^ joint 

 longer than 2"'^. Peraeopod 1 with small seta at apex of 7^^ joint. Peraeopod 2, 

 7^^ joint tipped with several setae, one very long, this joint longer than 

 the 6^^\ but shorter than either the 4*^ or the b^^. Peraeopods 3 — 5 with 

 7*ii joint minute. Peduncle of uropods as long as endopod, two-thirds of 

 the length of the exopod, with oblique series of setae on surface and several 

 setae on apical margin, some very long; second joint of endopod half as 

 long as P*, tipped with a strong spine; on the long outward curving exopod 

 there are many spines, passing distally into plumose setae. Colour brown. 

 L. about 4-5 mm. 



Enosima, Japan, depth 6 — 23 m. 



10. Fam. Diastyloididae 



1812 Diastyloididae, T. Stebbing in: Ann. S. Afr. Mus., u lOv p. 133, 146. 



Telson narrowly elongate, with only 2 apical spines. Antenna 1 with 

 slight flagella. Antenna 2 of female not strongly developed, flagellum in 

 male elongate. Mandibles with base of trunk broad. Exopods on peraeopods 

 1 — 4 in male, only on the first 2 pairs in female. Only 2 pairs of pleopods 

 in the male, the small rami of the 1^* both single- jointed, in the 2'^'^ confluent 

 to a single piece. Uropods with slender rami, the 3-jointed endopod not 

 differing much in length from the exopod. 



1 genus. 



1. Gen. Diastyloides 0. Sars 



1900 Diastyloides, G. 0. Sars in: Crust. Norway, v.3 p. 60 | 1900 D., Zimmer 

 iu: Fauna arctica, v.l p. 426, 431 | 1908 jD., Zimmer in: Ergeb. Tiefsee-Exp., u 8 p. 181, 

 182 I 1912 D., T. Stebbing in: Ann. S. Afr. Mus., v. 10 v p. 146. 



Eye wanting. Antenna 2 of female without apical plumose seta on 

 small terminal joint. Peraeopod 1 with 6*'» joint elongate. Peraeopod 2 

 with 2"^^ joint apically produced. 



2 species. 



Synopsis of species: 



J Carapace without pairs of oblique carinae 1. D. serratus 



\ Carapace with 2 pairs of oblique carinae 2. D. biplicatus 



1. D. serratus (0. Sars) 1865 Diastylis serrata, G. 0. Sars in: Forh. Selsk. 

 Christian., 1864 p. 169 1894 D. serratus, A.M.Norraan in: Ann. nat. Hist., ser.6 «.13p.276 | 

 1900 Diastyloides serrata, G. O. Sars, Crust. Norway, v. 3 p. 61 t. 45 | 1900 D. s., Zimmer 

 in: Fauna arctica, v. 1 p. 426 (with synonymy) | 1905 D. s., Caiman in: Sci. Invest. Fish. 

 Ireland, 1904 app. 1 p. 47. 



Pseudorostral lobes much produced, especially in 9 in which the acu- 

 minate tip is slightly depressed; antero-lateral corners obsolete. Carapace 

 smooth in 6, large "in Q with serrate lower margin and l)ranchial regions 

 roughened with minute forward pointing denticles; eyelobe minute. Pedi- 



