SYSTEMATIC ACCOUNT 265 



the Cape of Good Hope, the West Coast of Africa, the mid-Atlantic and the Humboldt 

 Current in the Pacific, specimens were obtained forming a series of intermediate forms 

 that made it impossible to recognize the value of the nomenclatural species and varieties. 

 All of the specimens observed have been referred to H. cuneiformis Wallich. 



Observed at Sts. 260, 294, 427, 434, 440, 451, 452, 675, 677, 679, 684; WS 705. 



Family ACTINODISCACEAE 

 Subfamily STICTODISCOIDEAE 



1. Cells without internal membrane. Cells flat, valves circular or polygonal, surface coarsely 

 punctate, radiate, furrows radiate Stictodiscus 



2. Cells with internal membrane. Cells flat, valves circular, coarse areolation in concentric 

 lines, furrows radiate Arachnoidiscus 



Subfamily ACTINOPTYCHOIDEAE 



1 . Cells solitary, valve surface divided into segments alternately raised and depressed 



Actinoptychus 



Subfamily ASTEROLAMPROIDEAE 



1. Cells circular, valve surface divided into sectors by radial extensions of hyaline central area; 



all sectors equal in size Asterolampra 



2. Cells circular, sometimes elliptical, surface divided into sectors by radial extensions of 

 hyaline central area ; sectors of unequal size ... ... ... ... ... Asteromphahts 



Subfamily STICTODISCOIDEAE 



Genus Stictodiscus Greville 

 Greville, 1861 



Stictodiscus affinis Castracane. 



Castracane, 1886, p. 119, pi. 1, fig. 4. 



Cells discoid, solitary, strong. Valves flat or nearly so, sometimes slightly depressed 

 at the centre. Valve covered with numerous strong radiating furrows. Furrows some- 

 times confluent, reaching to about half the radius, where they anastomose to form a 

 reticulate appearance over the central area of the valve. Lines of strong puncta are 

 arranged radially between the furrows. Puncta proceed from the margin of the valve, 

 but seldom penetrate far into the reticulate central area. Sometimes the central area is 

 furnished with one to three granules. Margin of valve strong, sharply curved down- 

 wards. Girdle simple, finely striate. Diameter of cell 80-200/u. 



This species has a wide distribution and has been observed frequently in Indian 

 Ocean material. It is probably a bottom form, usually epiphytic upon larger algae. It 

 was observed frequently in the material from the Bransfield Strait. This is the first 

 record of this species from the Antarctic. 



Observed at Sts. 664; WS 481. 



15-2 



