;j. REXIHORNERA, 19 



Var. j(3. TUBUiosA. (Plate XVIII. figs. 2, 4.) Oooecia represented 

 by an elongated dilatation in front of a branch ; surface 

 smooth. 



With respect to the last-mentioned form, I have considerable doubt 

 as to the propriety of associating it with H. violacea at all. It 

 forms, in fact, so marked a transitional form between Pustulopora 

 and Hornera that it might as reasonably be given to one as to the 

 other. The specimen from which I have made the figures and 

 taken the description was given to me many years since by my friend 

 Mr. Bowerbank, who informed me that it was procured by Captain 

 Beaufort in the North Atlantic in lat. 21° 35' N. and 90° 42' W., at 

 a depth of 20 fathoms. 



It difiers from H. violacea not only in its colour, which is brown, 

 but more importantly in the constitution of the oocecium, which in 

 no respect resembles that of the other species of Hornera with 

 which we are acquainted, but is exactly like that of Pustulopora, 

 Idmonea, &c. ; i. e. it is formed by a simple expansion of variable 

 size in front of a portion of a branch (Plate XVIII. fig. 2). Should 

 it be regarded as a species distinct from H. violacea {rar. proboscina), 

 it might be thus diagnosed : — 



Hornera tubulosa. 



Zoarium brown, irregularly dichotomous ; branches occasionally 

 inosculating ; zoocecia tubular, free for about half their length, 

 curved forwards and very long ; mouth orbicular, border even, some- 

 ■\vhat expanded; surface finely dotted, smooth, dorsal surface very 

 finely punctate ; oooecia formed by an elongated enlargement on 

 the front of a branch. 



3. RETIHORNERA, Kirchenpaur. 



Zoarium foliaceous, composed of subparallel branches connected 

 by transverse tubules, so as to form an expanded frond with qua- 

 drangular fenestrse. 



Retihomera (pars), Kirchenpaur, Catalogue iv. of the Museum Go- 



cleffroy, Hamburg, May 1869. 

 Hornera , ilf ' Gillivraij, Austr. Polyzoa. 



1. Retihomera foliacea, M'Gillivray. (Plate XIII. figs. 1, 2; 

 Plate XIX.) 



Zoarium irregularly plicate or convoluted, rising from a short 

 central stem with a discoid base ; branches very closely approxi- 

 mate ; the oblong fenestrae consequently are usually narrower than 

 the branches ; mouths of zoocecia exserted, margin toothed ; anterior 

 surface granular, numerous dehcate spines projecting into the 

 fenestrae ; dorsal surface granular, irregularly sulcate, or sometimes 

 nearly smooth ; oocecia unknown. 



