126 THE PLUMULARID^E. 



LYTOCARPUS RACEMIFERUS Allman. 

 (Plate XXXI, figs. 1-3.) 



Lytocarptts racemiferus ALLMAN, Challenger Report, Hyilroida, 1883, Pt. 1, p. 41, pi. xm. 



Trophosome. Colony attaining a height of about 12 inches; stein fascicled, much and irregu- 

 larly branched, main branches all directed toward one side of the stem; hydrocladia alternate, 

 scarcely exceeding one-tenth of an inch in length. HydrotheciH rather deep, margin serrated, 

 teeth blunt: intrathecal ridge well marked, situated near the fundus of the hydrotheca; mesial 

 nematophore adnate to the walls of the hydrotheca for nearly their entire height, and then con- 

 tinued as a short, blunt beak, which scarcely overtops the hydrotheca and has both a terminal 

 and a lateral orifice; lateral nematophores slightly overtopping the hydrotheca. 



Gonosome. Phylactocarps in the form of long racemes, laden with gonangia, springing from 

 certain branches of the trophosome at points near the origin of the branches from the stem, and 

 there taking the places of the proximal four or six hydrocladia, consisting of a series of internodes 

 having every internode provided with one median and two lateral spines, each of the proximal five 

 to eight iuternodes carrying also an ovate pedunculated gonangium. 



Dredged on" Bahia; depth, 10 to 20 fathoms. 



The above description is quoted entire from Allman. His figure shows that the gonaugia 

 take the place of hydrotheca?, and are more numerous than in other American species of Lyto- 

 carpnti. The arrangement of the nematophores on the phylactocarp suggests that the latter is 

 merely a hydrocladium, with the hydrotheca- obliterated on the distal portion and replaced by 

 gonangia on the proximal part. It differs, however, from the other species which I have seen in 

 the fact that there is no hydrotheca at the base of each phylactocarp. 



Type. In the South Kensington Museum, London. 



HALICORNARIA Busk (modified). 

 Halicornaria BUSK, Narrative, Voyage of H. M. S. liattlesnake, 1852, I, Appendix. 



Trophoaome. Stem not fascicled, no posterior intrathecal ridge; an anterior intrathecal ridge 

 usually present; hydrocladia not branched; hydrocladial internodes without septal ridges. 



Gonosomt: (lonangia borne on the stem or on the bases of the hydrocladia, not taking the 

 place of hydrothecii', and not protected by corbulte or phylactocarps of any description. 



As originally defined, this genus included all plumularians which did not have corbula-. In 

 1874 Allman 1 restricted the genus so as to include only "such Plumularid;e as possess the tropho- 

 some of Afjlaitphcniu, but have their gonangia destitute of corbnhe or other protection." In 1886 

 Bale 2 suggested that Alhnau's Halicornaria ramnUfern, a species witli accessory ram uli, should 

 be placed in a distinct genus. So far as I have been able to ascertain, none of the systematists 

 up to the present time have endeavored to find systematic characters in the trophosome by which 

 this genus can be recognized. The above combination of uoufascicled stem, absence of septal 

 ridges in the hydrocladial internodes, and the absence of a posterior intrathecal ridge, seems to be 

 sufficient to constitute good criteria for the genus. As here defined, Halicornaria approaches the 

 genus Nuditheca of this work, from which it differs in having unbranched hydrocladia and 

 gonangia borne on the stem or near the bases of the hydrocladia. In the only species of Halicor- 

 naria which has gonangia out on the hydrocladia, the gonaugia evidently take the place of hydro- 

 tbec;e, while in Nuditheca they do not. Halicornaria iiiitrata Allman J has a fascicled stem, strong 

 septal ridges in the hydrocladia, and a well-marked posterior iutrathecal ridge. The gonosome is 

 unknown, and its author regards its place in the genus Halicornaria as provisional. By the 

 present arrangement it would be excluded from the genus. 



All three of the American species of the genus Halicornaria are from the West Indian region, 

 and all are found in. comparatively shallow water. 



1 Report on the Hydroida collected during the expeditions of H. M. S. Porcupine, Transactions of the Zoological 

 Society, 1874, VIII, p. 476. 



-The Genera of the Plumulariidn-, 1886, p. 18. 



^Journal of the Liumean Society, London, 1885, XIX, p. 153, pi. XX. 



