256 Rev. T. Hincks on the 



It is undoubtedly a transition-form and one of tlie highest 

 interest. 



Avicularia are present under two forms — one placed laterally 

 and in mucli tlie same position as the similar appendao^e in 

 Notanim Inrsaria ; the other, which is much more highly deve- 

 loped, occupies a central place at the summit of each pair of 

 cells. 



The lateral avicularium is perfectly sessile and Is destitute 

 of the stem, which gives to that of our " Shepherd's purse 

 coralline " its striking resemblance to a tobacco-pipe. 



In other respects the two seem to agree, so far as my speci- 

 mens enable me to judge. In Synnotiim the lateral appendage 

 is only present on one of the cells in each pair, and occurs 

 alternately on the right and left of the zoarium ; it is placed 

 immediately above the top of the cell on the inner side and 

 close upon the double-stem, which embraces the pair of cells 

 below it. 



The second form of avicularium (the median) belongs to 

 the articulated division and is a fully developed " bird's head." 

 It is placed immediately above the pair of cells in the line of 

 their junction, and seems to be attached to the tubular con- 

 nexion by which the cells are linked together. It is borne 

 on a tall and rather stout peduncular support and is of a 

 globular shape (very slightly produced in front) ; the beak 

 terminates in a short, somewhat curved, spike-like extremity. 

 The peduncle on which the avicularium is borne is unlike the 

 ordinary form, and at first sight suggests a doubt whether 

 the appendage is movable (articulated) or merely peduncu- 

 late. I have met with a single case, however, in which it had 

 been swung back and remained with the oral surface turned 

 uppermost. 



The association of articulated avicularia with lower forms 

 in one and the same species is, 1 believe, a new fact. It is 

 interesting to remember that in Notamia we tind the fixed 

 form of the appendage, which probably comes " on the whole 

 nearest to the movable ' bird's head,' and constitutes the most 

 direct link between the two classes of aviculariuai." In the 

 present member of the Notamian family this fixed form has 

 been partially replaced by the higher, and the two develop- 

 mental stages stand side by side in the same organism. 



The differences between Notamia and Synnotum lie prima- 

 rily in the structure of the zooecium and secondarily in the 

 character and disposition of the avicularia. 



The name which 1 have adopted {Synnotum) was suggested 

 b}' Dr. Pieper as appropriate should his species prove to be 

 entitled to generic rank. 



