\i)0 



F'ig. 5. Lithohactruni forte. | n;itural size. 



5^. Vertical section showing in-current and ex-currenl 



canals. Natural size. 

 56. Section of skeleton showing canals. 

 5c-/. Monocrepid desmas, x 100. 

 5^. Amphityle, x 420. 



Fig. 6. Monanthn^ pluniosus in Pachastrella, var. tubiihitus. 

 f natural size. 

 6rt, Section of the same, f natural size. 

 66. Part of an oscular tube, slightly magnified. 

 6c. Monocrepid desma, x 100. 

 6d. Oxea^ x 100. 

 6e. Style, x 100. 



Fig. 7. Monanthiis plumosus on Pachastrella, sp. n. § natural 



size, 

 yrt. Vertical section, f natural size. 

 7/). (At lower right corner of plate) a slender oxea from 



the dermal membrane, x 100 (very probably foreign).* 



* Note. — The fact that the variety is designated as fig. 6 and the type as fig 

 7, while only the spicules of the var. are figured, is due to the discovery of a 

 second specimen of the " type " leading to an alteration of the author's views 

 after the plate had been printed off. 



[Published 27th May, 1903]. 



