. Discovery reports. Discovery (Ship); Scientific expeditions; Ocean; Antarctica; Falkland Islands. 238 DISCOVERY REPORTS where they predominated. Even at the intervening stations they ranked second only to the chaeto- cerids. The unavoidably heterogeneous nature of the group, however, was very evident. Whereas inshore the strongly neritic species Fragilaria karsteni predominated, along with Asterionella japonica, it was the oceanic Thalassiothrix longissima and panthalassic Nitzschia delicatissima that accounted for nearly all of the group totals farther out. The mid-intermediate line proved
. Discovery reports. Discovery (Ship); Scientific expeditions; Ocean; Antarctica; Falkland Islands. 238 DISCOVERY REPORTS where they predominated. Even at the intervening stations they ranked second only to the chaeto- cerids. The unavoidably heterogeneous nature of the group, however, was very evident. Whereas inshore the strongly neritic species Fragilaria karsteni predominated, along with Asterionella japonica, it was the oceanic Thalassiothrix longissima and panthalassic Nitzschia delicatissima that accounted for nearly all of the group totals farther out. The mid-intermediate line proved too short to extend beyond the rich coastal diatom zone. The estimated diatom totals were high throughout and very closely paralleled by the group-totals for the WS986. -D d D7 d d D4 d "W5990 WS|Wl WS992 WSW WS994 WS995 ⢠⢠TOTAL DIATOMS -⦠CHAETOCERACEAE â -' "PENNATAE' ». BIDDULPHIINEAE o DISCINEAE â SOLENIINEAE \ '" \ \ \V B X) IOO SEA MILES FROM LAND F'g- 75- Estimated total diatoms, and diatom group totals, survey I. A. Sylvia Hill line, io-ii March 1950. B. Southern Intermediate line, 11-12 March 1950. predominating chaetocerids. The other groups clearly fulfilled a minor role, much on the same level, with 'Pennatae' of some consequence inshore. Apart from the profusion of neritic Chaetoceros species, at least ten in number, the species of most importance were: Among the Discineae, inshore, Stephanopyxis turris diminishing rapidly as one proceeded seawards; and Thalassiosira sabtilis, which reached its highest numbers and relative importance at station WS 983. Among the Biddulphiineae, Eucampia zoodiacus at the two inshore stations only. Among the Soleniineae, Dactyliosolen mediterraneus and much lesser numbers of the more cosmo- politan Rhizosolenia spp. farther offshore. Among the ' Pennatae', Fragilaria Karsteni and Asterionella japonica inshore with Thalassiothrix longissima at station WS 984. On the Sylvia Hill and southern intermediate
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