SYSTEMATIC REPORT 153 



Mysidetes anomala sp.n. 



Occurrence: 1 ! S- 35 J) 



St. WS748. 16. ix. 31 (night). Magellan Strait, 30o(-o) m., 5 S3, largest 20 mm., 2 ??, larger 19-8 mm., frag- 

 ments. Types. 

 St. WS 749. 18. ix. 31 (day). Magellan Strait, 4o(-o) m., posterior end of large female. 



Remarks. This species so closely resembles M. patagonica that it will suffice to point out the 

 differences whereby they may be distinguished. 



General form. M. anomala is rather more slender with a longer tail-fan. Rostrum in both species is 

 acutely pointed, but in M. anomala its lateral margins are uptilted as they are in M. posthon. 



Antennular peduncle. The process from the outer distal angle of the first segment is shorter than in 

 M. patagonica and in only one specimen did it extend to the distal margin of the second segment. 



Antenna. The scale is considerably longer and more tapering than in M. patagonica (cf. Fig. 35 B 

 and F) and the dorsal spine of the sympod is larger than the ventral. 



Thoracic endopods longer and more slender. In Fig. 34 C and G I have figured on the same scale 

 the eighth thoracic appendage of an adult male of the same size of both species. Both specimens 

 appeared to be fully adult with dense setose brushes on the antennules. 



' Uropods. Though very alike in form and armature, the uropods in M. anomala are half as long again 

 as in specimens of the same size of M. patagonica and the exopod is more bowed. It should be noted 

 that the magnification of Fig. 35 D is greater than that of Fig. 35 H. 



Telson shorter than the sixth abdominal somite. Cleft relatively less deep than in M. patagonica, 

 being less than one-fourth of the total length of the telson, though the very long apical spines give 

 the appearance of greater depth. The armature of the apical lobes is the most striking character of this 

 species and is unlike that of any other species of the genus as yet known. The specimens appear to be 

 fully adult, but the lateral margins of the telson are unarmed on the proximal half of their length. The 

 spines arming the distal half are very large and strong, forming a regularly graduated series increasing 

 in size to the large apical spines, and extending round the broadly rounded apical lobes into the cleft 

 for fully two-thirds of its depth. The remaining third of the margin of the cleft is armed on each side 

 with 9-10 very small teeth (Fig. 35 J). 



Length of largest male, 20 mm.; female, 19-8 mm. 



Distribution. The species has been taken at two stations only, both in the Strait of Magellan. 



Mysidetes dimorpha sp.n. 



Occurrence: V s- .5 



St. 45. 6. iv. 26 (day). South Georgia, 238-270 m., fragments. 



St. 140. 23. xii. 26 (day). South Georgia, 122-136 m., fragments. 



St. 190. 24. iii. 27 (day). Palmer Archipelago, 93-126 m., fragments (doubtfully). 



St. MS 19. 9. iv. 25 (day). East Cumberland Bay, South Georgia, 120-80 m., fragments of imm. male. 



St. MS 23. 12. iv. 25 (day). East Cumberland Bay, 220-160 m., 1 adult ?, 14 mm., fragments. 



St. MS 62. 19. i. 26 (day). Wilson Harbour, South Georgia, 31 m., 1 <?, 4 ?$, all imm., largest 12 mm., fragments. 



St. MS 63. 24. ii. 26 (day). East Cumberland Bay, 23 m., 1 adult <J, 1 juv. 3, 7 adult ?$, largest 14 mm., 2 



juv. $$. $ Types. 

 St. MS 65. 28. ii. 26 (day). East Cumberland Bay, 39 m., 28 juv., largest 10 mm. 



St. MS 66. 28. ii. 26 (day). East Cumberland Bay, 18m., 3 adult S3, i3'2-i3-6mm., 67 juv., largest 10mm. <JTypes. 

 St. MS 67. 28. ii. 26 (day). East Cumberland Bay, 38 m., 1 juv., 9 mm. 

 St. MS 68. 2. iii. 26 (day). East Cumberland Bay, 220-247 m., 3 juv. 

 St. MS 74. 17. iii. 26 (day). East Cumberland Bay, 22-40 m., 1 adult $, 14 mm., 34 juv., largest 10-2 mm. 



