FIONA. 



inner side of each papilla. The anus is placed about half way down the back towards 

 the right side. The orifices of the generative organs are separate, placed near together 

 below the tentacles on the right side. 



The anatomy of this animal amply proves its generic distinctness. The tissues are very 

 tough and firm when compared with the other Eolididte, particularly the skin and the 

 cellular tissue uniting the viscera. The branchial papillae, too, are much more firmly attached 

 than usual, and require considerable force to remove them. 



The oral orifice is situated on the inferior surface of the head : it is small, and the 

 external lip is divided behind on the median line, much as in Eolis. The channel leading to 

 the buccal apparatus is very short and constricted. The buccal mass, (PL 38a, fig. 4a, and 

 fig. 5), is small, rather long, slender, and irregularly elliptical, the corneous plates (fig. 5c) 

 being visible at the sides : it is slightly prolonged behind, for the reception of the posterior 

 portion of the tongue, and the muscles are arranged as in Eolis. 



The tongue is supported on a fleshy ridge that rises up from the floor of the buccal 

 cavity, and extends in the antero-posterior direction from the oesophagus towards the anterior 

 opening. This organ is long, linear, and strap-formed, and is composed of forty transverse 

 semicircular plates of an orange colour, each (fig. 9) bearing a stoutish central spine and six 

 or seven smaller ones at the sides. All the spines are a little bent, and have their points 

 directed backwards towards the oesophageal opening. 



The corneous plates (fig. 6) are little short of the size of the buccal mass, and much 

 elongated, well arched and ovate ; and, when united and entirely isolated, strongly resemble 

 the valves of a minute Mytilus. They are smooth, glossy, and of a brownish amber colour, 

 darkest towards the anterior extremity, which gives support to the cutting blade {a). This 

 is a wing-like appendage, of no great size, terminating below in a free point, and having the 

 cutting margin arched forward, plain, and nearly at right angles to the general direction of 

 the plate ; above is a small process or fulcrum (5), the point at which the two plates are 

 articulated; and immediately behind this point the dorsal margin of the plates is reflected and 

 expanded into an arched lobe (<?), for muscular attachment. 



The oesophagus, (fig. 4, 6), is a short and rather slender tube, which, passing from the 

 upper aspect of the buccal mass towards its posterior extremity, opens into the anterior 

 margin of a distinct pyriform stomach (<?). This organ has the broad end forward, is placed 

 above the reproductive apparatus, and lies quite in the anterior portion of the visceral cavity. 

 The internal surface does not appear to be lamellated. The intestine {d), passes from the 

 posterior extremity of the stomach, and inclining slightly to the right side, passes back- 

 wards to the tubular anus, (fig. 2a), which is placed a little to the right of the median 

 line of the back, immediately behind the heart. The intestinal tube is rather short, of equal 

 diameter throughout, and internally plicated longitudinally. 



The hepatic apparatus is very peculiar in this animal. The pyloric extremity of the 

 stomach receives two biliary ducts (fig. 4 e e), one on each side of the intestine. These ducts, 

 or hepatic canals, are nearly as wide as the intestine, and, diverging as they leave the stomach, 

 very shortly pass into the skin at the sides of the back, where each opens into a wide 

 channel (/), that extends nearly the whole length of the body. The channels receive 

 numerous branches, which communicate with the glands of the papillae, and as they approach 

 the lateral expansion at the sides of the body, they appear to be subdivided several times. 



