88 DISCOVERY REPORTS 



Subfamily GASTROSACCINAE 



Genus Gastrosaccus Norman, 1868 



1868 Gastrosaccus Norman, p. 438. 



1872 Acanthocaris Sim, p. 4. 



1880 Haplostylus Kossmann, p. 95. 



1882 Pontomysis Czerniavsky, p. 79. 



1893 Chlamydopleon Ortmann, p. 23. 



Remarks. Norman (1868, p. 438) founded this genus for those mysids in which the pleura of the 



first abdominal somite in the female were produced to form part of the marsupium. The genus is 



otherwise characterized by having the outer margin of the antennal scale naked and ending in a thorn, 



the first and second pairs of pleopods of the male well-developed and biramous, third pair with the 



exopod extremely long and the endopod variable, telson with large apical cleft armed with spines and 



lateral margins also armed with spines, outer margin of the exopod of the uropod armed with spines 



and no setae, and the inner margin of the endopod armed with few or many spines. An interesting 



feature of the genus Gastrosaccus is the variation shown in the form of the posterior margin of the 



carapace. In some forms this is simply emarginate, but in others there may be a pair of median reflexed 



lobes or large quadrangular lobes, or there may be a number of filiform prolongations forming 



a fringe. 



Gastrosaccus sanctus (van Beneden), 1861 



1 861 Mysis sancta van Beneden, p. 27. 



1877 Gastrosaccus sanctus G. O. Sars, p. 64. 



1882a Gastrosaccus sanctus, Czerniavsky, 1, p. 85. 



1892 Gastrosaccus sanctus, Norman, p. 155. 



1 95 1 Gastrosaccus sanctus, Tattersall and Tattersall, p. 162. 



Occurrence : 

 St. 90. 10. vii. 26 (day). Off Simon's Town, South Africa, 10-12 m., 2 ?$, larger nearly adult, 11-5 mm. 

 St. 149. 10. i. 27 (day). Mouth of Cumberland Bay, South Georgia, 234-200 m., 1 damaged ?, estimated length 



11 mm. 

 St. 443. 23. ix. 30 (night). South of Knysna, South Africa, 49-0 m., 1 <J, 1 1 mm. 



St. WS 1000. 13. iii. 50 (night). About 100 miles west of Orange River estuary, 100-50 m., 1 very small juv. 

 St. WS 1002. 14. iii. 50. Eight miles out to sea off Orange River estuary, 50-0 m., 20 &J, 24 ?? ovig., largest 9 mm. ; 

 35° J uv - 3-7 mm - 



Remarks. These specimens do not differ in any essential from the published descriptions and figures 

 of G. sanctus. The well-developed reflexed lappets on the hinder margin of the carapace are rather 

 narrower than those I have seen in specimens from British waters and the spines arming the apical 

 lobes and lateral margins of the telson are unusually large, but I do not consider that these slight 

 differences are of specific importance. 



Distribution. This species is widely distributed in coastal waters of Europe, from the southern 

 parts of the North Sea, the British Isles, the Mediterranean to Suez and the Black Sea. It has been 

 recorded from the west coast of Morocco and from the west coast of Africa, as far south as Casablanca 

 Harbour and the Cameroons (Tattersall, 1927, p. 316). It has also been recorded from the Canary 

 Isles. The Discovery records from the extreme south of South Africa and from South Georgia very 

 considerably extend its known geographical range. 



G. sanctus is essentially a shallow water littoral form and has never been recorded from the open 

 ocean. It is markedly euryhaline in northern waters and in the Black Sea lives in a salinity as low as 

 18 % while in the Atlantic, near the Canary Islands, it has been found in salinities of 37 % . 



