Mr. J. Alder on new species of Sertularian Zoophytes. S55 



Halecium nanum. PI. XIV. 



Polypary creeping over the surface of Sargassum hacciferum 

 and forming an irregular network of fibres, throwing up short 

 stunted stems at each bifurcation or intersection. The stems 

 consist of little more than the tubular portion or pedicles of 

 the cells, which arise above each other in a zigzag order, each 

 springing alternately from the side of the last. The cells are 

 broad and shallow, and scarcely at all expanded at the rim. The 

 portion of the stem beneath each cell is nearly of the same width 

 as the latter, short, a little wrinkled at the base, and having a 

 single joint near its junction with the cell below. Frequently 

 there is only a single cell at each joint of the creeping fibre^ or 

 a succession of cells developed one within the other. The ovi- 

 capsules are very large, and generally set in clusters of two or 

 three together on the stem or the sides of the cells ; they are 

 irregularly ovate, bulging out more on one side than the other, 

 and terminated by an oblique aperture with two lips ; they are 

 fixed by short pedicles of two or three rings. Height of stem 

 seldom above y^jth of an inch. 



This curious little parasite of the Gulf-weed is worthy of no- 

 tice from its showing an interesting variation in size and form 

 in a genus of which so few species are yet known, and those 

 nearly all inhabiting the British shores. 



It appears to have hitherto escaped observation, unless it is 

 the " Campanularia "i" very imperfectly figured (but not described) 

 in Dana's ' Zoophytes of the United States' Exploring Expedi- 

 tion,' p. 690, pi. 61. f. 9. 



The specimen from which the present description and accom- 

 panying figures were taken was found on Gulf-weed collected 

 by Mr. William Wright in lat. M° 48' north and long. 34" 25' 

 west, and presented to me by his brother, Mr. Joseph Wright, 

 of the Newcastle Museum. 



EXPLANATION OF THE PLATES. 

 Plate XIL 



Figs. 1 & 2. Plumularia halecioides, natural size and magnified. 



Fiff. 3. A portion more highly magnified. 



Fig, 4. Ovicapsules. 



Fig. 5. A portion of the compound stem. 



Plate XIIL 



Fig. I. Halecium lahrosum, natural size. 

 Fig. 2. A portion magnified : a, capsules. 

 Fig. 3. A portion of a variety magnified. 



23* 



