170 discovery reports 



Occurrence : 



St. WS 89. 7. iv. 27 (day). Half-way between Falkland Is. and Staten I., 23-21 m., 2 adult ?$, 19 mm., 3 juv. <J<J, 



1 juv. $. 

 St. WS 749. 18. ix. 31 (day). Magellan Strait, 4o(-o) m., 77 $<$, largest 18 mm., 138 $$, ioovig., largest 19-5 mm., 



405 juv. 

 St. WS 834. 2. ii. 32 (day). Off north-east coast of Tierra del Fuego, 27-38 m., 4 adult <$$, largest 24 mm., 18 adult 



9$, largest 19-5 mm. 



Remarks. Hansen (1913, p. 21) referred an immature female from Port Albemarle, Falkland Isles, 

 to this species, although in some respects it did not agree with Zimmer's description and figures of 

 the types. I find in the large number of specimens, which I here refer to N. patagona, some characters 

 which agree with Zimmer's description and figures and some which more closely agree with Hansen's. 

 The outstanding characters of this species are the broad rostral plate with a median incision, the long, 

 very narrow telson with its lateral margins armed with a large number of equal spines, and the long 

 exopod of the uropods in which the distal five or six plumose setae of the outer margin have become 

 replaced by strong, finely plumose articulated spines (Fig. 42 J). Coifmann (1937, p. 13) added 

 another character, which I have been able to verify in all the specimens which I have examined, 

 namely : the distal plumose seta on the outer margin of the antennal scale has become modified into 

 a strong spine which, as far as I can see, is not plumed (Fig. 42 C). The specimens in the Discovery 

 collection all possess these specific characters and the differences which they show in the proportions 

 of the various parts I attribute to individual variation. 



The rostrum resembles Hansen's figure more closely than that of Zimmer. It is clearly divided by 

 a definite incision into two lobes and the appearance of a median cleft is heightened by a thickening 

 of the tissues in the middle line (Fig. 42 A). The antennal scale is nine times as long as broad and in 

 shape agrees very closely with Zimmer's description. Hansen's specimen had a more slender scale 

 especially in its distal half. The eyes are more robust and are more covered by the rostral plate than 

 in Hansen's specimen and agree more closely with Zimmer's figure. The maxilla is almost precisely 

 as figured by Hansen with the lobes from the second, third and fourth segments much more developed 

 than in Zimmer's figure and the outer setiferous lobe relatively smaller (Fig. 42 E). The numbers of 

 sub-segments in the carpo-propodus of the third to the eighth thoracic endopods show some variation, 

 but in almost all the specimens I have examined they are greater than described by Zimmer. He gave 

 the number as eight in the third pair of appendages and nine in the last. I have found that there are 

 usually ten in the anterior appendages and there may be as many as twelve in the last pair. On the 

 base of the sixth thoracic endopods in the females there is a small rudimentary oostegite similar to 

 that figured by me for Mysis stenolepis (in W. M. Tattersall, 195 1 , p. 173). Similar structures have been 

 noticed in a number of species of Neomysis and Acanthomysis and it is quite probable that they occur 

 in many other species, but have not been noticed by workers (Fig. 42 H). The endopods of the uropods 

 are shorter than the long telson, and my specimens differ from previous descriptions in having usually 

 three (rarely two) graduated spines on the ventral surface of the distal end of the statocyst. Zimmer 

 stated that there was only one spine in this position. The distal five or six setae of the outer margin of the 

 exopod are replaced by strong spines which are very finely plumose (Fig. 42 J). The telson is rather 

 longer and narrower than in either Zimmer's or Hansen's descriptions, the spines arming the lateral 

 margins are fewer and not so densely crowded towards the apex (Fig. 42 K). 



Distribution. Neomysis patagona has only been recorded from waters south of Patagonia and in 

 the Strait of Magellan, and the Discovery records do not extend its known geographical range. From 

 the large number of specimens taken at station WS 749 it is evidently a gregarious form, although it has 

 usually been taken only in small numbers. 



