K16 Mil. J. lUTf'Iin: ox HYDROIDS [Mmv 24, 



to 1)6 :u-r;ing(Ml in whorls, and of liu-ije. (lt-e[>ly stainalile cells in 

 the body-wall. 



The habit of this epizoon is peculiar, for, in addition to the 

 ordinary external meandering, the cfwnosarc may live within the 

 perisarcal tube of the hydroid upon which it grows. Thus in 

 several cases, the hydrothecae of this species project from within 

 the liydrothece of Idia pristis and Sertidarella quadridens. In 

 this respect much i-esemblance is shown to the habit of Lafoea 

 dispoliaiis, Warren (1909, p. 105), the wanderings of which 

 within the perisarc of its host, Sertidai-ia hklens Bale, have been 

 closely traced by Dr. AA^'arren. In the present case the material 

 being in a poor state of preservation, I have been unable to trace 

 the course of the parasite throughout. 



Dimensions :— 



Hydrotheca, length 0-53-0'84 mm. 



,, greatest diameter 0-21-0'27 mm. 



Peduncle, diameter 0-075-0-081 mm. 



Localities. St. 1, east of Tavoy Island and Port Owen, 4 to 12 

 fathoms, sand and broken shells, and m>id ; solitary hydrothecte 

 on Idia prisiis and SeriidarpUa quadridenti. St. 14, Bushlty 

 Island pearling-ground, shore to 21 fathoms, sand and mud; rare, 

 on Idia pristis. 8tt. 15 and 16, Ilavenshaw Island, Sir John 

 Malcolm Island, and Alligator Rock, 5 to 18 fathoms, rock and 

 sand, or rock and mud ; very rare, on Idia priistis. St. 23. Five 

 Islands, 8 to 12 fathoms, rock and sand, and mud ; very rare, on 

 Sertnlarella, quadridens. 



Hitherto this species h^s been found only on the western 

 sea-boai-d of the North Atlantic Ocean, and growing upon only 

 one host, Lytoscyphus viarginatus Allman : Loggerhead Key, 

 fathoms (Allman, 1877), 10 miles north of Zohlos Island 

 (Clarke, 1879), Anguilla, Antilles, 100-150 fathoms (Jiiderholm, 

 1903), off Bermuda, 30 fathoms (Ritchie, 1909«), and Prof. S. F. 

 Clarke, in litteris 1909, mentions its occurrence at West Florida, 

 20 fathoms, again on Li/toscj/phiis marginatus. 



Systematic position. - -The general appearance of the specimens 

 descri))ed as Lafoiia. vennsta resendiles that of a small parallel- 

 sided foirn of the exceedingly varial)le Campamdaria corrugata 

 Thornely. As the gonosomes of both species are unknown, and 

 even the hydi-anth of the former is undescribed, the difiiculties of 

 identification are thus grevlly increased. The present specimens 

 are, however, specilicaliy distinct from Campamdaria corriigata, 

 on account of the much smaller size of their hydrothecse, which 

 are ako more i-egularly I'inged, and are always cylindrical in 

 sha})e. Tlie hydi-anths also differ in shape and in structiire. 

 Those of the present specimens are more slender and possess 9 to 

 11, in place of 22 tentacles; they have a iriore hemispherical 

 hyposton)e, and lack the peculiar develojnnent of those endo- 

 dermal cells, which, in C. corriigata, project from the base of the 

 tentacles into the gjistric cavity, almost meeting there below the 



