HALOCORDYLE TIARELLA. 369 



*;j(.* IIalocobdtle tiakella, Aijres. 



Globiceps TIARELLA, — Ayves, in Proc. Bost. Soc. Nat. Hist., 1852, vol. iv, p. 193. 

 EucoRYNE ELEGANs, — Leidy , Marine Invert. Fauna of Rhode Island and New Jersey, 185,5, 



p. 4, pi. X, figs. 1 — 5. 

 Pennaria TIARELLA, — M'Crafhj, Gymnophtlial. Medusa;, Proc. Elliott Soc. Nat. Hist., vol. i, 



1857, p. 153. Alex. Ayassiz, IJlustr. Cntal., p. 187, figs. 



311—315. 



TROPHOSOME. — Hydrocaulus attainiug a height of four or five inches, main 

 stem nearly straiglit, alternately branched, branches distichous, sending off short, 

 sim])le, or slightly branched ramuli from their distal side ; main stem and branches 

 annulated at intervals, the ultimate ramuli annulated at their origin and termination. 

 Hydranths with about twelve fihform tentacles, in two verticils, having about six 

 tentacles in each. 



GONOSOME. — GoNOPHORES on short peduncles, developed just within the verticil 

 of filiform tentacles. Umbrella deep and narrow, marginal tentacles in the form of 

 four short conical processes. 



Colour. — Main stem and primary branches shining black, ultimate ramuli ochre-yellow ; 

 body of hydranth between the filiform and capitate sets of tentacles pink, encircled by two red 

 bands, the thin distal portion of the body translucent white. j\Iedus£e with the external surface 

 of the umbrella marked by four longitudinal red bands, each band lying directly over a radiating 

 canal; manubrium deep opaque red. 



Development of Gonosome. — Observed in August. 



Habitat. — Attached to Fuci shells, &c., in the sea. 



Bathymetrical distribution. — Laminarian zone. 



Locality. — Atlantic shores of North America, Ayres, Leidy, M'Crady, and A. Agassiz. 



Leidy has published an excellent description and figure of this beautiful hydroid. I have 

 never seen a specimen of it, and have availed myself of Leidy 's memoir in drawing up the 

 diagnosis here given. A very complete description of the medusa is also given by M'Crady, 

 who, however, refers the species to the genus Pennaria, in which he is followed by A. Agassiz, 

 ■who has also fully described the medusa and given us figures of it and of the hydranth. For 

 reasons already stated I cannot agree with M'Crady and A. Agassiz in referring it to Pennaria ; 

 I agree, on the other hand, with Professor L. Agassiz* in believing that it must constitute a 



^ 'Contr. Nat. Hist. U.S.,' vol. iv, p. 28]. 



