Cumacea: 11. Diastylidae, 1. Diastylis 91 



) Carapace mapped into polygonal areas by spines and spiriules 27. D. echinatus 



\ Carapace girdled by 3 nearly parallel ridges 28. D. tricinctus 



I Telsou scarcely half as long as peduncle of uropods . . . 29. D. nucella 



\ Telsou nearly as long as peduncle of uropods — 30. 



j Telsou with few lateral spinules 30. D. anomalus 



\ Telsou with many lateral spinules 31. D. asper 



1. D. bidentatus Calm. 1880 D. sp., Stuxberg in: Bih. Svenska Ak., v. 5 nr. 22 

 p. 29 ; 1882 D. sp., Stuxberg in: Vega-Exp., v. I p. 715 | 1882 D. picta, Stuxberg in: 

 A. M. Norman, Mus. Norm., p. 10 | 1912 D. bidentata, Caiman in: P. U. S. Mus , vAl 

 p. 605, 637 tf.45— 50 i 1912 D.pida, Caiman in: P. U.S.Mus., vAl p. 636 (corrected in litt.) 



In general like D. acoiyioides (nr. 23), but surface of carapace smoother, 

 the ridges very finely crenulated, only 4 oblique ridges on each side, the 

 2°'^ a little way from its lower end produced into a strong tooth pointing 

 sharply outward and forward, eyelobe carrying a few small denticles, and 

 frontal lobe 2 short transverse denticulated ridges; telson longer than peduncle 

 of uropods, its post-anal section much the longer with about 10 pairs of lateral 

 spines. Antenna 1, 3*^ joint longer than 2"<^, 1^*^ shorter than the 2 combined. 

 Antenna 2 of Q, penultimate joint elongate. Maxilliped 3, 2"*^ joint not 

 expanded distally, 3*^ wider than 4**^. Peraeopod 1, 2"^^ joint longer than rest 

 of limb, 5^^, 6th, c^^^ 7th subequal. Peraeopod 2, h^^ joint little longer than 

 6*'^ and 1^^ comliined. Exopod on 3^^ and A^^^ limbs of 9 rudimentary, 

 2-jointed. Endopod of uropods very slightly longer than exopod, about '^^|^^^^ 

 as long as the peduncle, 1^* joint nearly twice 2"'^ and 3^^ combined, spines 

 of medial margin respectively 10, 2, 2. Colour red and yellow (Stuxberg). 

 L. about 12 mm, in o varying from less to much more. 



At various stations of the „Alaskau area, including Aleutian Islands, and the 

 Pacific coast of N. America north of Puget Sound", from depths between 11 and 166 m. 



2. D. dalli Calm. 1912 D. d., Caiman in: P. U. S. Mus., vAl p. 605, 635 tf.40— 44. 



In general like I>. scorpioUies (nr. 23), but surface of carapace much 

 smoother, ridges not crenulated, only 4 oblique ridges on each side, the 

 2"^ not forming a prominent tooth, the pseudorostral lobes less produced than 

 in Ik bidentatus; telson a little shorter than the peduncle of the uropods, 

 post-anal section much the longer, lateral spines about 1 1 pairs. Antenna 1, 

 3^ joint longer than 2"'^\ 1^* than the 2 combined. Antenna 2 of 9, penul- 

 timate joint elongate. Maxilliped 3, 2°^^ joint not distally expanded, 3"^^ not 

 wider than P^. Peraeopod 1, 2^^ joint much longer than rest of limb, 5"' 

 a little shorter than 6*^ or 7*^ which are subequal. Peraeopod 2, 5^^ joint 

 a little longer than 6*^ and T^'i combined. Exopod on 3'^ and 4*^ limbs of 

 9 rudimentary, 2-jointed. Endopod of uropods very slightly longer than 

 the exopod, about half as long as the peduncle, 1^*^ joint much longer than 

 2"^'^ and 3'* combined, spines of medial margin respectively 9, 3, 2. L. 9 24 mm. 



Alaskan area, depth 24 — 146 m; Sea of Okhotsk, 137 m. 



3. D. planifrons Calm. 1912 D. p., Caiman in: P. U. S. Mus., vAl p. 605. 643 

 tf. 58—61. 



Pseudorostral lobes well produced, horizontal, acute, antero-lateral corner 

 obtuse. Carapace with prominent oblique ridge on each side starting from 

 the pseudorostral lobes and forming a prominent blunt tooth at its junction 

 with a curved ridge running up from the lower edge; to the rear the oblique 

 ridges meet a pair of convergent longitudinal ridges, while in front a blunt 



