816 MR. J. RITCHIE OS HYDROIDS [Maj' 24, 



to be arranged in wlioHs, and of large, deeply stainable cells in 

 the body-wall. . 



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

 ordinary external meandering, the coenosarc may live withm the 

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

 several cases, the hydiothecfe of this species project from within 

 the hydrothecie of Idia pristis and Sertularella quadridens. In 

 this respect much resemblance is shown to the habit of Lafoea 

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

 within tlie perisarc of its host, Sertidaria hidens Bale, have been 

 closely traced by Dr. Warren. 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 mud ; solitary hydrothecfe 

 on Idia prislis and Sertularella quadridens. St. 14, Bushby 

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

 on Idia pristis." Stt. 15 and 16, Ravenshaw Island, Sir John 

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

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

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

 Sertularella quadridens. 



Hitherto this species has been found only on the western 

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

 one ho.st, Lytoscyphus marginatus Allman : Loggerhead Key, 

 9 fathoms (Allman, 1877), 10 miles north of Zoblos Island 

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

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

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

 20 fathoms, again on Lytoscyphiis marginatus. 



Systematic position. — The general appearance of the specimens 

 described as Lafoea venusta resembles that of a small pai-allel- 

 sided form of the exceedingly variable Campanularia corrugata 

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

 even the hydranth of the former is undescribed, the difficulties of 

 identification are thus greatly increased. The present specimens 

 are, however, specifically distinct from Campanularia cwrugata, 

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

 are also more regularly ringed, and are always cylindrical in 

 shape. The hydranths also differ in shape and in structure. 

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

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

 hypostome, and lack the peculiar development of those endo- 

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

 tentacles into the gastric cavity, almost meeting there below the 

 [18] 



