CORBLLA OVATA. 33 



species, are disposed in a scattered radiating manner 

 at the margins, but are confined to the upper portions; 

 they partake of the colour of the mantle though they 

 are a little darker. A few smaller radiating fibres are 

 observed at the upper margin of the left-hand side. 



The branchial sac (fig. 35) extends nearly to the 

 bottom of the mantle, overlapping the right-hand side 

 of the visceral mass ; the spirals are remarkable for 

 the fewness of their coils, there being usually two, 

 rarely three, and they are stout and project boldly 

 upwards ; the longitudinal bars are delicate and cord- 

 like, with the suspended membrane deep; the papillary 





< 



FIG. 35. Part of branchial sac of Corella ovata. Miich enlarged. 



membranes are well developed, and have the free 

 border only slightly thickened, and not projected into 

 tentacular points or papilla?. There are about 36 

 oral filaments (PL XXII, fig. 11) which occasionally 

 vary a little in length ; they are wide at the base 

 where the margins are sometimes a little undulated, 

 and they rather suddenly attenuate upwards and are 

 produced and pointed at the extremity. The branchial 

 tubercle is a simple loop open in front above and 

 pointed behind. 



The disposition of the alimentary canal differs in no 

 respect from that of the type form ; the stomach is 

 well marked and rounded, the oesophagus constricted 

 and well produced ; the intestine bends downwards in 

 the usual manner and passes along the bottom of the 

 sac to the ventral margin, which it ascends almost to 



ir. 3 



