56 



AMERICAN HYDROIDS. 

 Distribution of Plumularia. 



The above table clearly shows that the West Indiaii region is the American center of distribu- 

 tion for this genus. The bathyinetrical table shows that the great bulk of the species is found in 

 shallow water, that the region from 20 to 100 fathoms seems poor in species, while that from 100 

 to 500 is represented by a good percentage of species. It must be remembered, however, that, in 

 order to make a fair comparison of the life at various depths the same number of hauls should 

 be made at each depth. 



PLUMULARIA SETACEA (Ellis). 

 (Plate, I, figs. 1, 4.) 



Corallina setacea ELLIS, Nat. Hist. Corallines, 1755, p. 19. 

 Sertularia xctacea PALLAS, Kleuchus /oophytoriun, 1766, p. 148. 

 Sertttlaria selacea ELLIS, Nat. Hist. Zoophytes, 1786, p. 47. 

 Sertularia setacea TURTON, Brit. Fauna, 1801, p. 216. 

 Plumularia setacea LAMARCK, Auim. sans Vert., 1st ed., 1815, p. 129. 

 Aglaoplieiiia selacea LAMOUROUX, Hist. Polyp. Flex., 1816, p. 172. 

 Plumularia selacea LAMARCK, Anim. sans Vert., 2d eel., II, 1836, p. 165. 

 Plumularia setacea. DE BI.AINVII.LK, Manuel d'Actinol., 1836, p. 477. 

 Plumularia setacea JOHNSTON, Brit. Zooph., 2d ed., I, 1847, p. 97. 

 Aglaoplienia setacea GRAY, Brit. Radiata, 1848, p. 80. 



Plumularia setacea Louis AGASSIZ, Cent. Nat. Hist. IT. S., IV, 1862, p. 358. 

 Plumularia setacea HINCKS, Brit. Hydroid Zoopli., 1868, p. 296. 

 And all subsequent writers consulted. 



Trophosome. Colony attaining a height of i! inches, usually unbranched; stem nonfascicled 

 and divided into internodes, each of which bears a hydrocladium on a process from its distal end; 

 hydrocladia alternate, proximal internode .short, without hydrotheca or nematophore, next inter- 

 node hydrothecate and the remainder of the hydrocladium composed of alternate hydrothecate 

 and intermediate internodes; nodal joints often accompanied by one or two internal annulations. 

 Hydrothecse rather shallow, cup shaped, and more closely approximated than usual ; nematophores 

 small, the supracalyciue pair overtopping the hydrotheca 1 ; a mesial ueuiatophore ui the base of 



