BY T. WHITELEGGE. 345 



The slit which indicates the formation of a new cell invariably 

 has an avicularium below, with the mandible pointing downward 

 at first, but as growth goes on this is usually forced to one side of 

 the moutli, though occasionally it remains in front. 



(6.) B. UMBONATA, Haswell. 



Eschara umhonata, Haswell, op. cit., p. 41, pi. II, figs. 5-6. 



Zoarium free, bilaminate, flat, simple or forming trilobate ex- 

 pansions, " surface ornamented with numerous rounded knobs of 

 various sizes," zooecia immersed, directed towards (what appears to 

 be the base) the primary part of the zoarium. Oral aperture 

 rounded above, and a wide sinus below ; peristomial orifice nearly 

 round, margin slightly elevated, with a subcircular pore on the 

 upper border ; an avicularium on each side of the mouth, frequently 

 a third one in front, mandible triangular generally pointing up- 

 wards. 



Zoc— Holborn Island, (20 fathoms). 



There are three specimens in the collection of the Australian 

 Museum, one a flat piece ^ of an inch by ^ of an inch : the other 

 two have each three lobes ; the central one in the larger specimen 

 is fg from base to summit, and the lateral lobes ^ of an inch in 

 length, and nearly as wide ; all the lobes taper a little outwards. 

 The " semilunar slit " is not seen in any of the specimens, but the 

 peristomial opening is, I believe, formed in the same manner as in 

 the others ; several of the zooecial openings are closed by a calcar. 

 eous plate, and have the appearance of young zooecia ; the plate is 

 seen to be thinner at the margin ; probably the slit-like opening is 

 not formed. 



Mr. Haswell's description of the mouth of this species clearly 

 shows that it was the anterior pore which he mentions as the sinus 

 in the lower lip. He says " mouth varying in form, the lower lip 

 sometimes straight, sometimes with a small sinus, sometimes with 

 a rounded central lobe." This exactly describes the appearance 

 of the anterior oi^al pore in various stages of perfection. The 

 peristomial orifice with the pore broken down closely resembles the 



