289 



Bracebridgia pyriformis Busk. 

 Mucronella pyriformis Busi<, Challenger, Zoology, Vol. X, Part I, p. 155, 



PI. XX, figs. 5 a, 5 b. 

 Bracebridgia pyriformis Mac Gillivray, Trans, and Proc. R. Soc. Victoria, 



Vol. XXII, 1880 (for 1885), p. 135, PI. II, figs. (J, 7. 

 (PI. XIV, fi-^s. ,3a-3e). 



The zooecia, which are as a rule pear-shaped or vase-like and have a circle 

 of widely separated pores somewhat distant from the margin, show over almost 

 the whole of the frontal surface a sharp, wavy, transverse striation appearing in 

 a number of broad, rounded ridges, somewhat curved and running mainly in the 

 longitudinal direction of the zooecium. One of these runs round the whole of the 

 zocecium, whilst another, which encircles the aperture, continues proximally to 

 this as two keels running side by side, which finally run together into one. Be- 

 tween the marginal and the median ridges there are also one or several on each 

 side, and sometimes we can distinguish a number which run obli(iuely inwards 

 and are partially separated by the pores mentioned. The only part of the frontal 

 wall of the zofecium which does not show this characteristic striation is a small, 

 depressed, semicircular or triangular region just i)roximally to the aperture. 

 Mac (lillivray has once found an avicularium on this spot. The primary aper- 

 ture, which has two small hinge-teeth, has a rounded, quadrangular form, and 

 the two lateral margins slightly converging distally meet in an arch, whilst the 

 proximal rim is slightly concave. The well-chitinized operculum is provided on 

 each side of the proximal part with a short muscular ridge. Outside the primary 

 aperture there is a low, but broad, somewhat trapeziform tooth, and between it 

 and the secondary aperture a small, stout, conical projection. The secondary aper- 

 ture is of an elongated, oval form and surrounded by a collar-like rim. 



Gonozooecia have not been found. 



The avicularia (fig. 3 c) appear on the margins of the colony in a more or 

 less interrupted row. They are stout, strongly arched, with a rounded, trapezium- 

 shai)ed circumference and provided with a fairly short, rounded triangular 

 mandible (fig. 3 d), which has its point directed towards the distal part of the 

 branch. 



The colonies are two-layered, branched with compressed branches. 



A fragment from Victoria. 



10 



