324 PERIGONIMUS MINUTUS. 



is probably a mere ovcrsiglit. In order to avoid furtlicr confusion I liavc followed llincks in 

 adopting Wright's specific name of " repens.'' 



I have never met with this species, and the diagnosis here given is framed from Dr. Wright's 

 description. 



3. Perigonimits minutus, Allman. 



Plate XI, figs. 4— (5. 



Perigonimus minutus, — Allman, in Anu. Nat. Hist, for January, 1863. 



TROPHOSOME. — Htdeocaulus consisting of simple stems which rise at intervals 

 from a creeping stolon and attain a height of one eighth of an inch ; peuisakc smooth. 

 Htdeanths with seven or eight, rarely twelve, tentacles, which are held straight but 

 very irregularly in extension ; body of hydranth partially invested by a cup-like exten- 

 sion of the perisarc. 



GONOSOME. — GoNOPHOiiES borne upon long peduncles, which spring at various 

 heights from the hydrocaulus. Medusa with the umbrella contracted towards the 

 summit, so as to give it a conical form ; two opposite marginal bulbs large, each 

 carrying a very extensile tentacle, two alternate bulbs much smaller and without 

 tentacles ; manubrium short, with the margin of the mouth fom--lobed. 



Co/o?o-— Hydranth ash-brown, manubrium and marginal bulbs of medusa ash-brown, 

 perisarc yellowish-brown. 



Development of Gonosome. — August. 



Habitat. — Forming a fringe round the operculum of Tarriiella communis. 



Bathymetrical distrihution. — Coralline zone. 



Locality. — Busta Voe, Shetland. 



The present species comes \'ery near to the Perii/onimus {Atracfylis) rejjcns of Wright, and, 

 indeed, is regarded by llincks as identical with it. It differs from it, however, in the irregular 

 disposition of the tentacles of the hydranth, and in the form of the medusa, which in Dr. Wright's 

 species shows no approach to the conical form of Periyonimus minutus, while it further differs 

 from it in the long peduncles which support the gonophores. 



The tentacles of the medusa are very extensile ; when contracted they are, like many other 

 species of Perigonimus, rolled into a spiral. 



Perigonimus minutus was abundant in the only locality where it has been as yet obtained, 

 and where it was entirely confined to the operculum of living Turritellas. Out of nearly thirty 

 specimens of Tmritella communis which I had dredged in Busta Voe and examined, not one was 

 free from this remarkable little hydroid. 



