240 DISCOVERY REPORTS 



tion. South and east of the Falkland Islands group there is an absence of records, but 

 here the continental shelf is narrow and waters of a suitable depth are limited, whilst 

 similarly the depth of the region south-west of these islands precludes the occurrence of 

 this species. Only one station on the Burdwood Bank yields a record, but imperfect 

 exploration of this uncongenial trawling ground makes its distribution here problematic. 



In the northern part, the area of the survey is cut across by a zone of absence running 

 east from the Gulf of San Jorge ; this zone separates the southern region already de- 

 scribed from a northern region of rich abundance where large numbers were taken in each 

 haul of the trawl. West of this rich region can be seen indications of a northward con- 

 tinuation of the longitudinal barren strip running parallel to the coast. 



This description of the distribution of M. subrugosa is, as stated above, based almost 

 entirely on the results of the 193 1-2 survey. The two previous surveys, more restricted 

 in every way, add little to the foregoing conclusions but tend to corroborate them. On 

 the first survey M. subrugosa was taken north and north-east of the Falkland Islands 

 and off the Patagonian coast. The central barren area was indicated. The second survey, 

 carried out with especial reference to the edge of the continental shelf, helps to show the 

 influence of depth on the distribution. 



The causes of the discontinuous distribution described above have not been ascer- 

 tained. The areas of concentration or absence appear to have no relationship to the 

 character of the substratum upon which they live. Matthews (1934) has mapped the 

 texture of the bottom deposits obtained on the 193 1-2 survey and M. subrugosa occurs 

 indiscriminately on all the grades which he distinguishes. The hydrological features of 

 the area are simple and comparatively uniform (Klaehn, 191 1). Only the Falkland 

 current has a direct influence in this region, and the only deviation from the simple 

 northward sweep of this water is the small and insignificant counter-current moving 

 southwards along the Patagonian coast. Again, no relationship between the hydrological 

 element in the environment and the above outlined distribution is to be found. 



MUNIDA GREGARIA 



The distribution of this species is remarkable for its neritic character, and the chart 

 (Fig. 18) shows the manner in which the species surrounds the Falkland Islands and 

 does not occur far from shore. The northern coasts and the entrances to Falkland Sound 

 seem to be favoured localities. Away from the Falkland Islands the species clings close 

 to the coast of Patagonia and Tierra del Fuego. The R.R.S. 'Discovery' took large 

 numbers in the harbours of Hermite Island and Cape Horn, and these records, no 

 doubt, indicate the extreme southern limit. 



Occurrences along the Tierra del Fuegian and Patagonian coasts are well marked and 

 doubtless the species is to be found all along this coast, close inshore, until the northern 

 limit is reached. The capture of M. gregaria at St. WS 771, 42° 40' S, 60° 32' W, is the 

 most northerly record of the species in this region. In addition to the records obtained 

 by the ships of the Discovery Committee, the observations of Captain Fagerli, of the 

 whale factory ship 'Ernesto Tornquist', in the Gulf of San Jorge and southwards from 



