Mr. J. D. Macdonald on Phyllirrhoe bucephala. 139 



very existence of the animals composing it, have been matters of 

 doubt to zoologists, during a late cruise to the Fiji Islands I deter- 

 mined to ply the towing-net with a little more diligence than usual, 

 hoping to obtain a few of these almost hypothetical beings, and was 

 rewarded by the capture of many specimens. 



Some were taken in the neighbourhood of Lord Howe's Island, 

 S. lat. 31° 31", E. long. 159° 5", some near Norfolk Island, S. lat. 

 29° 2", E. long. 168° 2", and others, although in smaller numbers, 

 in different parts of our track. They generally made their appear- 

 ance after dusk in the evening, and presented a great diversity in 

 size, form and other external characters, which is due to changes in 

 the muscular system, a variable amount of pigment-spots, &c. In- 

 deed at first I fully believed that several distinct species had been 

 brought up together, but this idea was abandoned when I observed 

 the most dissimilar forms gradually assume so close a resemblance 

 to each other, as ultimately to render it difficult to distinguish them. 



From these facts I am much inclined to think that the three spe- 

 cies described by Quoy and Gaimard, viz. P. umboinensis, P. piinc- 

 tulata and P. rubra, P. Lichtensteinii {Eurydice Lichtetisteinii of 

 Eschscholtz) and P. rosea of D'Orbigny, are all referable to Peron's 

 original species P. bucephala. 



The body of Phyllirrhoe is elongated in form and compressed 

 laterally, presenting for description an anterior and posterior extre- 

 mity, a right and left surface, and a dorsal and ventral border. The 

 head is surmounted by two lengthy, somewhat flattened and acumi- 

 nate tentacula; the eyes lie beneath the skin, not being visible ex- 

 ternally, and the mouth is in the form of a short truncated proboscis, 

 with a vertical opening. The oval-shaped body is on an average 

 about one inch and a half in length, which is something over twice 

 the measurement from the dorsal to the ventral border taken at the 

 middle or broadest part. The tail is quadrilateral in figure, gradu- 

 ally widening towards its posterior border, which is exceedingly 

 thin. The outer integument is perfectly transparent and lined by 

 muscular bundles, disposed longitudinally, and somewhat more than 

 their own breadth apart. These communicate with one another by 

 oblique branching slips, which thus form a kind of network enclosing 

 long lozenge-shaped spaces. Here and there nerve-trunks of con- 

 siderable size accompany the longitudinal bundles, dividing off into 

 smaller twigs, which distribute themselves at pretty equal distances 

 in a direction more or less perpendicular to that of the muscular 

 fibres. Scattered about at irregular intervals amongst these struc- 

 tures are numei'ous reddish-brow-n pigment-spots, in the centre of 

 each of which a clear vesicle is generally distinguishable. As above 

 alluded to, the actual tint of this pigment, and the relative number 

 of spots deposited within a certain space, determine both the general 

 quality and the depth of colour wliich are found to vary so much in 

 different sjiccimens of Phyllirrhoe. 



The alimentary canal of this creature consists of a muscular tube 

 lined with mucous membrane, extending without flexure from the 

 mouth to the vent. It commences anteriorly in an oral dilatation, 



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