27 o DISCOVERY REPORTS 



Asteromphalus Hookerii Ehrenberg. 



Ehrenberg, 1844 b, p. 200, fig. 3. 



Gran, 1905, p. 45, fig. 50. 



Lebour, 1930, p. 52, fig. 28 b. 



Asteromphalus Buchii Ehrenberg, 1844 b, p. 200, fig. 4. 



Asteromphalus Cuvierii Ehrenberg, 18446, p. 200, fig. 7. 



Asteromphalus Hutnboldtii Ehrenberg, 1844 b, p. 200, fig. 6. 



Cells discoid, solitary, small. Valves somewhat convex, undulate. Hyaline area in the 

 centre of the valve, occupying about one-half the total diameter of the valve surface. 

 Hyaline rays proceed from the central area to the periphery dividing the valve into 

 sectors. Rays five to seven in number, usually narrow. The rays are of equal length, but 

 one is much narrower than the others. A system of radiating branched or zigzag lines 

 traverse the central area, joining the apices of the peripheral sectors. Peripheral sectors 

 areolate, areoles fine, arranged in tangential lines. Sectors not rounded towards the 

 centre of the valve. Areoles of uniform size throughout. The hyaline rays terminate at 

 the margin of the valve in a small process. Diameter of valve 44-60^. 



This species has a wide distribution in temperate and subpolar seas. Common around 

 South Georgia, often occurring in large numbers. Oceanic. 



Observed at Sts. 261, 339, 365, 368, 378, 381, 382, 384, 386, 461, 475, 477, 478, 479, 

 480, 570, 577, 578, 580, 619, 661, 666, 1362; WS 481, 545, 549, 550, 551, 552A, 631 ; 

 MS 86. 



Asteromphalus parvulus Karsten. 

 Karsten, 1905, p. 90, pi. 8, fig. 14. 



Cells discoid, solitary, small. Valves slightly convex. Hyaline area in the centre of the 

 valve, very large, occupying one-half to three-quarters of the total diameter of the valve 

 surface. Hyaline rays proceed from the central area to the periphery. Rays usually six 

 in number and mostly wide, but one is always very narrow. Peripheral sectors wide, 

 punctate. Puncta rather coarse, considering the size of the organism, and arranged in 

 tangential lines. The central hyaline area is traversed by a number of radiating branched 

 or zigzag lines, which join the apices of the punctate sectors. Apices of the sectors not 

 straight or rounded but bearing a median depression. Hyaline rays terminate at the 

 margin of the valve in a very small and indistinct process. A narrow hyaline margin 

 surrounds the valve. Chromatophores : several small rounded bodies. Diameter of 

 valve 22-40 p. 



This species is very like A. heptactis, but is quite distinct from it. A very small 

 species favouring cold water of low salinity. Observed frequently in the Bellingshausen 

 Sea and Drake Straits, but never in great numbers. Oceanic. 



Observed at Sts. 368, 378, 379, 380, 381, 382, 383, 384, 575, 576, 577. 



Asteromphalus Roperianus Ralfs ex Pritchard. 



Pritchard, 1861, p. 838. 



Karsten, 1905, p. 90, pi. 8, fig. 8. 



Asterolampra Roperiana Greville, i860, p. 120, pi. 4, fig. 14. 



