378 Prof. Allman on the Construction and 



minute polypoid trophosome, which he describes as bearing a close 

 resemblance to the Campanularia raridentata. Alder. See Wright 

 in Micr. Journ. n. s. vol. ii. 



Thaumantias inconspicua, Forbes. 



LeptoscyphidaB. 

 1. Leptoscyphus*, Allman, nov. gen. 



Trophosome. — Hydrocaulus simple or branching, attached by 

 a creeping filiform hydrorhiza ; hydrothecse with an operculum 

 composed of converging lanceolate segments. Polypites cylin- 

 drical when extended; tentacula surrounding the base of a 

 conical metastome. 



Gonosome. — Gonophores phanerocodonic. Umbrella, at the 

 time of liberation, deep bell-shaped or conical ; manubrium 

 pendent from a conical projection from the roof of the umbrella, 

 of moderate size, with the mouth surrounded by four short capi- 

 tate tentacula; radiating canals four, each terminating distally 

 in a bulb, without evident ocellus, each bulb giving origin to a 

 cluster of two or three tentacles; a single marginal tentacle 

 with a bulbous base is also developed from the centre of each 

 interradial space. 



I constitute the genus Leptoscyphus for a very minute Hydroid 

 which I discovered some years ago in Orkney, where it occurs rather 

 abundantly, creeping over the fronds of Laminaria digitata. I have 

 already described it (Ann. Nat. Hist. Nov. 1859) under the name of 

 Laomedea tenuis ; but its remarkable Medusa, as well as the general 

 characters of the trophosome, must certainly separate it from that 

 genus. It will be noticed that the Medusa belongs to the type which 

 is destitute of lithocysts, and has its generative elements developed in 

 the walls of the manubrium, thus affording one of the two known 

 exceptions to the rule that the Medusae of the Campanularian Hy- 

 droids are of the type which carry lithocysts on the margin of the 

 umbrella, and have their generative elements developed in special 

 sexual buds which arise from the radiating canals, — the other excep- 

 tion occurring in the Medusa which Agassiz has referred to Lafoea 

 cornuta, Lamx.f 



It will also be seen that the Medusa of Leptoscyphus resembles in 

 all essential points the form for which Forbes has constructed his 

 genus Lizzia ; and I have little doubt that, when mature, its charac- 

 ters would entirely correspond with this medusal type. I should 

 accordingly have had no hesitation in assigning to the present Hy- 

 droid the name of Lizzia, instead of constituting for it a new genus, 

 were it not that Claparede has found, in an undoubted Lizzia, that 



* From XfTTTor, delicate, and (rKv(f)os, a cup. 



f Thaumantias, though a Campanularian, is destitute of lithocysts, but 

 its sexual buds are developed from the radiating canals. 



