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



broad mesenteries ; central stomach and basal stomach fused, without distinct pyloric 

 stricture. Four horizontal groups of filaments, simple or double, bush-shaped or brush- 

 shaped, limited to the interradial corners of the bottom of the stomach. 



The genus Charybdea, the oldest known genus of this family and order, was 

 founded by Peron in 1809, with the following indefinite diagnosis : — "La concavity de 

 l'estomac se confondant avec celle de l'ombrelle ; rebord garni de faux bras, ou 

 plutot de faux tentacles" (Tableau des Meduses, &c, Annal. Mus. H. N., vol. xxiv. 

 p. 332). Peron united in this genus two entirely different Acraspeda, both of which 

 he knew only very superficially and incompletely — the Mediterranean Charybdea 

 marsupialis and the secmatorial Atlantic Charybdea periphylla. The latter was 

 first seperated by Steenstrup and raised to be the representative of the genus 

 Periphylla. On the other hand, the genus Charybdea was retained by almost all 

 new authors for the known Charybdea marsupalis of the Mediterranean, which had 

 already been described and figured by Plancus in 1739, as " urtica soluta marsupium 

 referens," and of which Milne-Edwards had given a very full (though for the most part 

 mistaken) description in 1833. Quite recently (1879) Claus gave a very detailed 

 histological monograph of this type of the genus Charybdea. I was myself able 

 to examine several new species of this genus, and to re-describe its character more 

 minutely. In the sense which I have retained here, those Charybdeidae which have 

 a suspended velarium (with canals and frenula) belong to the Charybdea. Charybdea 

 is distinguished from the genus most nearly related {Tamoya) by the flat, low pouch- 

 shaped stomach, the narrow mesenteric folds, and, specially, by the formation of the 

 gastral filaments. These are distributed horizontally in the four perradial corners of 

 the bottom of the stomach, as four simple or double pencil-shaped or brush-shaped 

 groups of filaments, whilst in Tamoya they extend as four vertical bands in the inter- 

 radial lateral lines of the large depending gastral sac. The deep-sea species described 

 below is, on the whole, nearly related to the Mediterranean Charybdea marsupialis, 

 which is only half the size, but is distinguished from it by the broader velum, containing 

 twice as many velar canals, which are also much more richly dendritic. Moreover, the 

 sculpture of the exumbreUa is different. The histological conditions have been 

 described in great detail by Claus in his monograph on Charybdea marsupialis; we shall 

 therefore confine ourselves to a short account of the organological peculiarities, giving 

 special prominence to the specific differences shown between Charybdea murrayana and 

 Charybdea marsupialis. There may perhaps be sufficient to justify this species being 

 taken as the representative of a separate genus : Charybdusa. I have named this 

 species in honour of my friend John Murray, first assistant in the Challenger 

 Commission. 



