100 THE VOYAGE OF H.M.S. CHALLENGER. 



Genus 30. Bassia, 1 Quoy et Gaimard, 1827. 

 Bassia, Quoy et Gaimard, MS. (compare Lesson, Aealephes, p. 451). 



Definition. — Diphyidse with two angular, pyramidal or prismatic nectophores of 

 different size and form. The basal nectophore is four-sided pyramidal, asymmetrical, and 

 much larger than the symmetrical apical nectophore. Bracts, four-sided prismatic and 

 wedge-shaped below, with an ovate, ascending phyllocyst, and an odd descending canal 

 arising from its base (Sphenoides, Genus 15). 



The genus Bassia was founded by Quoy and Gaimard in 1827 for a Diphyid which 

 they found in Bass Strait, and called, from its four-sided nectophore, Bassia quadri- 

 latera. The majority of later authors have called it Abyla quadrilatera (following 

 Blainville, 24), or Abyla bassensis, following Huxley, who gave an excellent description 

 of it in 1859 (9, p. 45). Another species, from the Tropical Atlantic, taken oif the coast 

 of Guinea, was described at the same time very accurately by Gegenbaur under the name 

 Abyla perforata (10, p. 26, figs. 20, 21). I myself have observed a third species in the 

 Indian Ocean (Bassia tetragona), and a fourth species, different from the three others, 

 in the Canary Islands, Bassia obeliscus. Since the latter also occurs in a bottle in the 

 Challenger collection, taken in the Northern Atlantic, near the Azores (Station 354, 

 May 6, 1876), I give its special description here, and the figures which I drew in 1867 

 from living sjjecimens in Lanzerote. Bassia differs from Abyla (with trigonal necto- 

 phore) and Calpe (with pentagonal nectophore) in the tetragonal shape of its distal 

 nectophore, which retains better the original form of a quadrilateral Medusa-umbrella. It 

 differs further in the peculiar form of its wedge-shaped hydrophyllia and Eudoxire, which 

 are free Sphenoides (p. 116) with an odd basal canal descending from the phyllocyst. 



Bassia obeliscus, n. sp. (Pis. XXXVII., XXXVIIL). 



Abyla obeliscus, Hkl., 1867, MS. Canar. 



Habitat. — Northern Atlantic ; Station 354, south of the Azores, west of the Canary 

 Islands, May 6, 1876 ; hit. 32° 41' N, long. 36° 6' W. Surface. 

 Canary Islands, Lanzerote, February 1867 (Haeckel). 



Nectophores. — The two nectophores united are 12 to 16 mm. long, 5 to 7 mm. 

 broad ; they are very different in form and size. The distal or posterior nectophore is 

 10 to 12 mm. long, 5 to 7 mm. broad; twice as long and broad as the proximal or 

 anterior. The ground-form of the latter is symmetrical, that of the former asymmetrical. 



Apical Nectophore (fig. 5 seen from the ventral face, fig. 6 from the dorsal face, 

 fig. 7 from the coryphal edge or the original top, fig. 8 from the basal face). — The apical 



1 Bassia= Inhabitant of Bass Strait. 



