92 Cumacea: 11. Diastylidae, 1. Diastylis 



median ridge runs between them. Pedigerous segment 5 with hind corners 

 acute, little produced; telson about -/g^^ as long as peduncle of uropods, its 

 post-anal section the shorter, with 5 pairs of lateral spines. Eye with 3 corneal 

 lenses. Maxilliped 3, 2»'i joint much widened distally, produced into a small 

 lobe laterally, 4*^^ wider than 3'\ produced into a curved tooth laterally. 

 Peraeopod 1, 5*^ joint longer than 6"\ Peraeopod 2, 5"^ joint nearly twice 

 as long as 6*^ and 7*^ combined. Exopod on 3'^ and 4^^^ limbs of o rudi- 

 mentary, 2-jointed. Exopod of uropods half as long as the peduncle, a little 

 longer "than the endopod, in which the V^ joint is longer than the 3^, the 

 3'^ than the 2'''\ the 2 combined rather longer than the I'S spines of the 

 medial margin respectively 6, 4. 4. L. 9 14 mm. 



S. America, lat. 51 <> 34' S.. long. 68» W., 91 m; Straits of Magellau, 112 m. 



4. D. alaskensis Calm. 1912 D. a., Caiman in: P. U. S. Mus., *;. 41 p. (305, 641 

 tf. 51—57. 



Pseudorostral lobes much and acutely produced. Carapace narrowing 

 forwards, more or less completely encircled by 6 transverse ridges in the 9 , 

 the 6^^ obscure in the tf, the hind margin upturned. Ey el obe rather longer 

 than broad; hinder angles of b^^ pedigerous segment blunt; pleon segments 1, 

 2, of d each with a medio-ventral spine; telson rather less than '^j/^ as long 

 as peduncle of the uropods, post-anal section the longer, with about 6 pairs 

 of lateral spines. Antenna 1, 2"^ joint shorter than 3^^. Antenna 2 of Q , 

 penultimate joint elongate. Maxilliped 3, 2^'^ joint expanded distally, 3'^ narrower 

 than 4t'\ Peraeopod 1, 2^^ joint about as long as rest of limb, 6^^ longer 

 than 5*11 ^y jt\ Peraeopod 2, 5^^' joint much longer than 6*^ and 1^^ comluned. 

 Exopod on 3"^ and 4*'^ limbs of Q minute, 2-jointed. Exopod of uropod a 

 little less than half as long as the peduncle, and slightly longer than the 

 endopod, which has the 1^* joint equal to 2"fi and 3*1 combined, or less. 

 spines on medial margin respectively 4, 2, 2. L. 9 13-o mm, d 10-6 mm, 



Alaskan area, depth 9 — 110 m. 



5. D. anderssoni Zimmer 1907 D. a., Zimmer in: Zool. Anz., r. .31 p. 220 | 

 1909 D. a., Zimmer in: Ergeb. Schwed. Siidpol.-Exp., r. 6 nr. 3 p. 18 t. 6 f. 97— 105, 

 t. 7 f. 106—118. 



Pseudorostral lobes well produced in front of the eyelobe, which in 9 

 but not in d carries a pair of denticles, frontal lobe crossed by 2 ridges 

 in 9, 1 in d, these being followed by 10 more or less encircling ridges, 

 of which the first 1 and the last 2 are less developed than the rest; they 

 are finely denticulate, as is also the upturned hind margin. The upper hind 

 margin of the first 2 pleon segments is finely dentate; the telson almost as 

 long as the 5*^ pleon segment in 9, longer in the d, with post- anal section 

 much the longer, carrying 8 or 9 pairs of lateral spines in 9, about 17 in d. 

 Eyelobe showing lenses but no pigment. Antenna 1, P* joint longer than 

 2"*^ and 3'i combined. Maxilliped 3, 2'"^i joint more than twice as long as 

 rest of limb, 3'i much wider than base of 4*''. Peraeopod 1, 2"^^ joint not as 

 long as rest of limb, 5**1 rather shorter than 6*^, 6*^ much shorter than 7*^. 

 Peraeopod 2, 6*^ joint about ^j./^ of 7*^, both together about -//^ of 5*^' 

 Exopods of 3'^ and 4*^ pairs minute 2-jointed in 9, strongly developed in d. 

 Setae on medial margin of peduncle in the pleopods clearly modified as 

 retinacula. Peduncle of uropods as long as 5"' and 6*^ pleon segments 

 combined, with about 26 spines on medial margin in 9, many more in d, 

 the rami rather more than a third as long, the exopod a little the shorter 



