IOO DISCOVERY REPORTS 



Genus Submargarita Strebel, 1908 

 Type (monotypy) : Submargarita impervia Strebel 

 Submargarita impervia Strebel 



Submargarita impervia Strebel, 1908, p. 75, pi. 5, fig. -jia-c. 

 Submargarita impervia Thiele, 1912, p. 188, pi. 15, fig. 18 (radula). 



Dentition. Fig. G, 10, p. 189. 



Type locality. Cumberland Bay, 252-310 m., South Georgia. 

 St. 27. West Cumberland Bay, 3-3 miles 44 E of Jason Lt., South Georgia, 15 Mar. 1926, no m. (one example). 



Genus Antimargarita n.g. 

 Type: Valvatella dalcis Smith 



This is provided for thin-shelled, colourless, elaborately sculptured depressed-turbinate species with a 

 wide, deep, steep-sided umbilicus. The dentition (Eales, 1923, p. 7, fig. 4) resembles that of Margarita in 

 the evenly arcuate sweep of the laterals and central, but individually these teeth are of very different shape. 



The simple coiled shells of the Trochoids mask a diversity of internal structures in an ancient and 

 primitive group. Thiele (1921, p. 68) has shown this in his valuable researches on the dentition. 



On shells alone there would be every excuse for classing together such species as Valvatella dulcis 

 Smith, Margarita gemma Smith and Solariella kempi n.sp. All three are thin-shelled, umbilicated, and 

 elaborately sculptured with crisp spiral ridges and axial threads, but the dentition clearly indicates that 

 not only are three genera required for their reception, but also they fall individually into three distinct 

 subfamilies of the Trochacea. 



The genus probably includes Submargarita smithiana Hedley (1916, p. 38, PI. 5, fig. 58) from off 

 Shackleton Ice-shelf, 65 20' S, 95 27' E, in 240 fathoms, and Minolia thielei Hedley (loc. cit.) from 

 near Shackleton Ice-shelf, 64 32' S, 97 20' E in no fathoms. 



Antimargarita dulcis (Smith) 



Valvatella dulcis Smith, 1907, p. 10, pi. 11, fig. 8. 

 Margarites dulcis Thiele, 1912, p. 190, pi. n, fig. 21. 

 Margarites dulcis Smith, 191 5, p. 63. 

 Minolia dulcis Hedley, 1916, p. 38. 

 Margarites dulcis Eales, 1923, p. 6. 



Type locality. Discovery Winter Quarters, McMurdo Sound, 77 50' 50" S, 166 44' 45" E, 130 

 fathoms. 



St. 175. Bransfield Strait, South Shetlands, 63 17' 20" S, 59 48' 15" W, 2 Mar. 1927, 200 m. 

 St. 1660. Ross Sea, 74 46-4' S, 178 23-4' E, 27 Jan. 1936, 351 m. 



Dentition. Fig. G, 5, p. 189 (after Eales, 1923). 



Range. Ross Sea ('Discovery'), Adelie Land (Smith, 1907, 1915), Gauss Station (Thiele, 1912), 

 South Shetlands ('Discovery'), 130-400 fathoms. The 'Discovery' records extend the range of this 

 species to three-fourths of the circumference of Antarctica. 



Antimargarita thielei (Hedley) 



1916. Minolia thielei Hedley, Aust. Antarct. Exped. (ser. C), iv (1), Moll. p. 39, pi. 5, fig. 59. 

 Type locality. Near the Shackleton Ice-shelf, 64 32' S, 97 20' E, no fathoms. 



St. 1652. Ross Sea. 75 56' 2" S, 178 35' 5" W, 23 Jan. 1936, 567 m. 

 The largest example from St. 1652 has 3^ whorls and is 3-8 mm. in diameter by 3-4 mm. in height. 

 The type has four whorls and measures 8x7 mm. 



