REPORT ON THE HYDROIDA. 53 



parietal fold ; Intrathecal ridge obsolete ; mesial nematopliore adnate to the hydrothecal 

 walls for the entire height of the walls, and then projected as a strong curved spine for 

 about the same height ; lateral nematophores wide, conical. 



Gonosome not known. 



Halicornaria plumosa is a singularly beautiful species. Though it is highly probable 

 that I have correctly referred it to the genus Halicornaria, this determination cannot, 

 in the aljscnce of the gonosome, be regarded as otherwise than provisional. 



One of its most striking features is seen in the very long mesial nematophore, which 

 is adnate to the anterior wall of the hydrotheca for its entire height, and is then 

 continued as a long, curved, horn-like spine for nearly the same distance. The margin 

 of the hydrotheca, instead of presenting the serrated condition usual in the Statoplean 

 Plumularidse, is seen, when view^ed in profile, to have a deep obliquely^directed notch on 

 each side, but is otherwise destitute of serration. The deep fold in the anterior w^alls of 

 the hydrotheca, though occurring in other species, is also characteristic. 



In its long mesial nematophore it presents a character in which it would agree with 

 Kirchenpauer's Macrorhyncliia section or sub-genus of Aglaophenia. For reasons, how- 

 ever, abeady mentioned," the Macvorhynchia of Kirchenpauer can scarcely be accepted as 

 a definite group. 



The present species appears to come near to the Halicornaria speciosa of the Gulf 

 Stream exploration.^ In general habit there is a close agreement between the two, 

 while in both the wide hydrotheca has an anterior parietal fold, and its margin — though 

 in the Gulf Stream species this does not present the deep lateral notch of Halicornaria 

 plumosa — is in both destitute of true serration, being in Halicornaria speciosa merely 

 crenate. The mesial nematophore, however, in Halicornaria speciosa is not continued 

 beyond the margin of the hydrotheca in the form of the long, curved, beak-like process 

 seen in Halicornaria plumosa. 



That the Gulf Stream species is a true Halicornaria there is no doubt, for the gono- 

 some was present in the specimens examined, and removed all difficulty as to generic 

 identification. 



Dredged at Station 122, September 10, 1873, off Barra Grande, Brazil, from a depth 

 of 32 fathoms. 



Azygoplon, nov. gen. 



Name from aZ^Cyos, uiijJaired, and ottA.oi', a weapon, in allusion to tlie aljsence of the lateral 

 nematophores. 



Genekic Character. Trophosome. — Hydrocladia pinnately disposed. Mesial nema- 

 tophore adnate to the walls of the hydrotheca ; no lateral nematophores. 



' See above, p. 47. 



= HydroiiU of Gulf Stream, p. 54, pi. .\x.\is'. 



