86 On SomeJSew Species of Catenicella and Dictyopora ; 



same "basis. The polyzoary is thin, fan-shaped, somewhat 

 contorted. The plates are about four inches high, and the 

 broadest is about the same width. The separate flexible 

 stems are up to an inch long, and from an eighth to a quarter 

 of an inch wide. To one of the plates there is a secondary 

 plate attached, at an acute angle, and in another there are 

 several plates so arranged as to form two compartments, one 

 very small, the other two inches deep, half an inch wide in 

 one diameter, and one and a-quarter in the other at the 

 orifice. In all, slightly raised ridges extend, dividing from 

 the stem to a variable distance up the plate. The fenestra are 

 of a considerable size, 1J to 3 mm. wide, the intervening 

 spaces about 4 mm. 



The cells are arranged in oblique lines. They are trape- 

 zoid, broad, and more or less rounded above, much attenuated 

 below. The mouth is circular, or nearly so. Below the 

 mouth and about the middle of the cell there is frequently 

 an avicularium, with a small triangular mandible directed 

 obliquely upwards, with a deep pit at its base. In many 

 cells there is only a large round pore, without any mandible. 

 The surface of the cell is somewhat raised on each side of 

 the avicularian pit (frequently more so on one side), and 

 towards the sides of the mouth. It is obscurely pitted. The 

 margin of the foramina is nearly plain, and not divided 

 into distinct, abortive cells or nodules, as in D. grisea and 

 cellulosa. 



The structure of the cells in Kirchenpauer's Adeona 

 arborescens seems to resemble that of the present species. 

 They are, however, sufficiently distinguished by the pro- 

 longations of the stem in the frond, which, in the former, are 

 very thick and prominent, and extend for a long distance on 

 the polyzoary, while in D. Wilsoni they are short and very 

 slightly elevated. 



Port Phillip Heads, Mr. J. B. Wilson. 



D. alhida var avicularis. 

 I have examined two imperfect specimens of a species 

 seemingly identical with Adeona cdbida (Kirchenp.), but 

 having a number of large avicularia round the borders of the 

 fenestras, which could scarcely have been overlooked by 

 Dr. Kirchenpauer. I propose to name it D. alhida var 

 avicidaris. One specimen is four inches by two, the other 

 rather narrower. Both are broken, and want the stem. The 

 polyzoary is twisted and cellular, like that of D. cellulosa. 



