W. II. HARRIS OX ]*rARIXB MICROSCOPIC VEGETAnLF. ORGANISMS. 157 



the generic term ; and probably, when more is known regarding the entire 

 group, a separate genus may be created for such forms. 



Very rare. Challenf/e)' Station No. 23, off Sombrero Island, West Indies, 

 450 fathoms. Plate 9, Fig. 5 x 300. 



Genus Achlya. 



Aclihja fase'icnJata. — This is a rather minute organism ; typical examples 

 are generally deeply immersed within the shell ; the branches radiate 

 from a central point in every direction, they divide dichotomously at 

 frequent intervals, and when fully developed form compact little spherical 

 bundles. 



Sometimes the plants occur near the surface of the containing fragment ; 

 they are then outspread, forming circular patches ; the filaments are much 

 crowded, but they do not become confluent. 



No appendages are visible. 



Widely distributed. Not uncommon in dredgings from foreign localities ; 

 rather rare in material from the British coasts. 



Acldya monile. — A small and very interesting organism ; it is highly 

 branched ; the filaments in their early stage of growth have a distinctly 

 septate appearance (probably illusory), but as they mature this feature 

 becomes more prominent by the enlargement into bead-like cavities, which 

 are sometimes contiguous, at others slightly separated. 



The filaments are rather large in diameter tov the size of the plant, 

 and they have a tendency to erode the surface of the shell. Devoid of 

 appendages. 



Very rare. Typical specimens have lieen found in recent material from 

 Lagos Bay, S. Australia, and in Miocene deposit from Auckland, New 

 Zealand. Plate 9, Fig. 6 x 300. 



Achlya radmia. — An easily recognised species. The filaments arise from 

 a small circular cavity ; at first they are few in number ; they divide 

 dichotomously but sparingly, and taper gradually towards their extremities ; 

 they are of considerable length. 



The plants occupy a superficial position in the containing fragments, and 

 they appear to be devoid of special means for contact with the water. 



Very rare. Fine specimens were obtained from Java Sea, 45 fathoms, 

 doubtful examples from the Cornish and Welsh coasts, and very small plants 

 in Miocene material from France. 



Acldya tortnosa. — This is a very complicated form ; to convey a correct 

 idea, by words alone, is rather difficult. 



In some instances there are indications that the organism consists of 

 filaments of two distinct forms, but whether this is a permanent feature or 

 not, I am at present unable to state. 



The most striking characteristic is the manner the filaments wander in 

 every conceivable direction in a zigzag way, and at the same time forming 

 graceful curves, completely covering the surface of the shell and yet not 

 becoming confluent ; sometimes these branches may be seen to arise from 



