Zoology.-] NATURAL HISTORY OF VICTORIA. [Polyzoa. 



Plate 95, Figs. 12-16. 

 RETEPORA FISSA (P. McG.). 



Description. — Polyzoary expanded, waved, or slightly convoluted; fenestrse 

 oval ; cells rhomboidal or elongated, separated by raised lines ; mouth rounded 

 above, lower lip hollowed, entire, or with a slight sinus and loop-shaped mark or 

 groove about the centre; operculum rounded, broader than high; an avicularium 

 near the middle of the cell, with the triangular mandible directed downwards, or 

 downwards and outwards ; ovicell large, rounded, prominent, with a vertical fissure, 

 wider above, closed below; posterior surface with numerous slightly prominent 

 vibices and a few small avicularia. 



Reference.— P. H. MacGillivray, Tr. Roy. Soc. Vict., 1869, 1882, and 1883; 

 R. marsupiata ?, Smith, Floridan Bryozoa. 



This species, which is probably not uncommon, varies consider- 

 ably. In young specimens the interspaces are slender, with from 

 1 to 3 or 4 rows of cells ; the fenestrse being large and wide, giving 

 to the whole a more open appearance. Older specimens are much 

 more calcareous, the fenestrse comparatively smaller, and the poly- 

 zoary altogether more massive. In the most developed specimens 

 the mouth has the lower lip nearly straight or hollowed, entire, or 

 with an obscure sinus from which extends downwards a short 

 groove. In more slender specimens the cells are longer and 

 narrower ; the upper part of the cell is curved forwards, the 

 mouth nearly circular, and opening upwards. From the centre of 

 the lower lip a shallow groove, with slightly raised edges, extends 

 vertically downwards ; immediately below this, or slightly to one 

 side, is usually an avicularium, with a bluntly triangular mandible 

 directed downwards and tilted somewhat forwards. The lower 

 lip on either side of the groove is smooth or sometimes serrated. 

 The edges of the groove occasionally meet to form a tube 

 extending its whole length, or confined to the lower end. The 

 avicularium on the front of the cell is frequently situated on an 

 elevation which is sometimes of enormous size ; the mandible is 

 then much larger and more acutely pointed. Sometimes there are 

 more than one avicularium on a cell. 



Dec. x. [ 17 ] c 



