2'26 THE VOYAGE OF H.M.S. CHALLENGER. 



gonostyles on the internodes, scattered between the siphons. Tentilla tricornuate, 

 with a terminal ampulla and two paired horns. 



The genus Agalma was established by Eschscholtz in 1825 for a new Physophorid 

 which he had observed living in the Northern Pacific (21, p. 743, Taf. v. fig. 17, and 1, 

 p. 150, Taf. xiii. fig. l). The figure and description are very accurate, and this Agalma 

 okenii must therefore be retained as the permanent type of the genus. It is closely 

 allied to Crystallodes, but distinguished from this by the loose cormidia and the 

 formation of a peculiar hydrcecium in the axis of the siphosome ; the thick bracts are 

 here so arranged that they enclose together a central cavity into which the contracted 

 stem with the cormidia may be retracted. Eschscholtz had already pointed out this 

 peculiar character as an essential difference from the similar Stcphanomia. The same 

 characteristic structure is very obvious in the new Indian species, which is described in 

 the sequel as Agalma eschscholtzii (PL XVIII. figs. 8-17). A comparison of its loose 

 cormidia with the ordinate cormidia of Crystallodes (PI. XVII.) Ulustrates their 

 distinction ; the siphons and tentacles in this latter issue separately between the bracts, in 

 a ventral series ; whilst they issue in the former, crowded in a bunch, from the basal 

 ostium of the hydrcecium. The same seems to be the case in three other species of this 

 genus, which are described by Dana as Crystcdlomia polygonata (North Pacific, 73, p. 459), 

 by Huxley as Agalma breve (9, pi. vii.), and by Leuckart as Agalma clavatum (8, Taf. 

 xiii. figs. 1-6). Later authors have described as Agalma a number of Agalmidse which 

 belong to other genera of this family. 



Agalma eschscholtzii, n. sp. (PI. XVIII. figs. 8-17). 



Habitat. — Indian Ocean, Ceylon (Belligemma), December 1881 (Haeckel). 



Nectosome (fig. 8, upper half). — The swimming apparatus, in the single specimen 

 observed, was composed of an apical pneumatophore, and two opposite rows of necto- 

 phores, four in each row, besides some buds of undeveloped nectophores at the apex of 

 the tubular trunk, at the base of the pneumatophore. The trunk was undulating, 

 nearly zigzag, of a yellowish colour. The length of the nectosome is 40 mm., the 

 sagittal axis 30 and the frontal axis 20 mm. 



Pneumatophore (fig. 8). — The float is ovate or pyriform, about half as long as a 

 nectophore, and covered with purple pigment-cells in the upper or apical half. The 

 lower or distal half is yellowish, and exhibits eight equidistant longitudinal lines, the 

 insertions of the eight vertical septa which divide the pericystic cavity of the pneuma- 

 tophore into eight radial pouches. 



Nectop>hores (fig. 8, lateral view ; fig. 9, dorsal view). — The nectophores have 

 the form of a broad and flat wedge, with a deep median incision on the two-horned 



