[62] MR. JAMES RITCHIE ON HTDROIDS [May 28. 



Tliis operculum is frequently drawn within the hydrotheca. The 

 aperture faces obliquely upwards. 



The gonosome is absent. 



Locality. Creeping upon a leaf found in one of the bottles 

 containing Mr. Crossland's collection of tunicates from Mattiota, 

 St. Vincent Harbour, Cape Verde Islands. 



The peculiarly shaped hydrothecaj in the present specimen bear 

 some resemlilance to those of Sertularia lucernaria Eirchen. 

 1864 ; but in that species the aperture is almost horizontal, with 

 a very distinct margin, the hydrothecse are widely separated, 

 and the colonies are branched, with a bushy habit of growth, 

 altogether different from the minute, simple, and scattered 

 colonies of S. Icevhnarginata. 



Family Phimulariid.s:. 

 Plcmularia halecioides Alder 1859. 



This .species is represented by a few specimens, attaining a 

 maximum height of 2'5 cm., which agi-ee closely with the de- 

 scription of Hincks (1868). The following variations from and 

 additions to that description were noted : — The branches, which 

 are rare and may arise on any side, sjiring in the .specimen.s 

 examined, not from the original h3'droclade-bearing tube, but 

 from one of the secondary tubes of the .stem- fascicle ; the hj'dro- 

 clades bear up to six hydrothecie in place of Hincks's maximum 

 of four ; intermediate athecate internodes are not always pre.sent 

 between thecate inteinodes, thus in 100 iritemodes examined 

 only 31 were athecate and intermediate, a pair of the latter 

 rarely occurring together ; the gonangia, for the most part 

 strongly ringed, occur not only on the stem but also on the hydro- 

 rhizal tubes. Similar variations have been noted by Billard 

 (1904, pp. 181 et seq.) in specimens from the French coast and 

 from Algeria. 



Locality. St. Vincent, Cape Verde Islands : growing on the 

 bottom of a lighter; 20th July, 1904. Also found on 22nd 

 July, 1904, by diving among coral in a depth of 2 fathoms. 



MoNosTiEcnAS quadeidens (McCrady 1857). (Plate XXV. 

 fig- 4.) 



Two colonies have been referred to this .species. They differ 

 markedly in size and habit from the flabellate, dichotomously 

 branched, 6-inch high specimens described by Nutting (1900, 

 p. 75) ; for they are unbranched and but 1 cm. in height. Never- 

 theless the minute structure agi-ees so closely ivith Nutting's 

 descriptions and figures, that I cannot regard these specimens as 

 specifically distinct. I noted, however : — (1) The peculiar manner 

 in which the hydroclades arise from the stem. The distal 

 portion of the stem-internode bends over towards the anterior 

 aspect of the stem, and to the end of this bent portion the hydro- 

 clade is attached bv a slanting node ; while from the posterior 

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