REPORT ON THE RADIOLARIA. 919 



striped (the expression of concentric lamellae), and with spinulate surface, covered with innumerable 

 small thorns. The basal quarter of each spine is straight and simple, the second quarter twice 

 forked, and these four fork-branches are again in the outer half of the spine richly forked or 

 ramified, with diverging, slightly curved thin branches ; each of the twelve spines with about sixty 

 to eighty terminal branches, the ends of which seem to fall into a spherical face. The position of 

 this remarkable species in this family is doubtful 



Dimensions. Length of the spines 012 to 016, of the simple basal part 0'04. 



Habitat. South Pacific (off Juan Fernandez), Station 299, surface. 



5. Polyplagia viminaria, n. sp. 



Numerous (sixteen to twenty or more) radial spines of about equal size, arising from a common 

 central point and diverging in different directions, richly and more or less irregularly branched. 

 The ends of the numerous small branches seem to fall into a spherical face. The large spines of 

 this species have the same form and structure as in the preceding, nearly allied species, but are 

 more numerous and more irregularly branched and disposed. 



Dimensions. Length of the spines 0'2 to 0'25, of the simple basal part 0'05. 



Habitat. North Pacific, Station 241, surface. 



Family XL VII. PLECTANIDA, Haeckel. 



Plectanida, Haeckel, 1881, Prodromus, p. 424. 



Definition. P lectoidea with a wattled skeleton, composed of the meeting and 

 united branches of radial spines, which arise from a common central point or central rod, 

 and protect the partly enclosed central capsule. 



The family Plectanida comprises those NASSELLARIA in which the skeleton is 

 composed of radial spines, arising from a common centre, and of a loose wickerwork, 

 produced by concrescence of the meeting branches of those spines. This rudimentary 

 wattled skeleton is either quite irregular or only slightly regular, but it never assumes 

 the form of a complete lattice-shell, as in the Cyrtellaria (the Spyroidea, 

 Botryodea, and Cyrtoidea), nor does it exhibit a ring (as in the Stephoidea). 

 The central capsule is partly or wholly protected, and often entirely enclosed by the 

 wattled skeleton. 



Three species only of Plectanida have been hitherto known. The first described form 

 is Plectophora arachnoides, which its discoverer Claparede observed in a living state in 

 1855 on the western coast of Norway, and considered as a mere variety of his Plagia- 

 cantha arachnoides. Two other species were afterwards observed in the Mediterranean, 

 Polyplecta dumetum, 1856, by Johannes Miiller (united by him with Acanthodesmia) 

 and Polyplecta polybrocha by myself in 1864. Many new forms are found in the 



