Mr. J. U. Macdonald on Phyllirrhoe bucephala. 457 



I felt justified in trustinn^ to what seemed my very distinct recollection 

 of its sense. I hud the less hesitation in doing this, as in M. \'ogt's 

 subsequently published ' Zoologische Briefe*,' he gives the received 

 interpretation to the parts of the so-called 'hearts' without any in- 

 dication of a change of opinion. 



I make this statement in explanation of what might otherwise 

 seem to be great carelessness on my part, and for the purpose of 

 further pointing out that M. Vogt not having made the supposed 

 discovery, it is quite impossible that Professor Owen's researches 

 should have been suggested by it. 



April 26. — Sir Benjamin Brodie, Bart., V.P., in the Chair. 



" Observations on the Anatomy and Affinities of the Phyllirrhoe 

 bucephala (Peron)." Bv John Denis Macdonald, Esq., R.N., As- 

 sistant-Surgeon of H.M.S.V. ' Torch.' 



As the true position of Peron's genus PhyUirrhoe, and even the 

 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 otliers, 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 obser\-ed 

 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. amboinensis . P. pi/nc- 

 tnlata and P. rubra, P. Lichtensteinii {Eurydice Lichtensteinii 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 t"ne 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- 



* Frankfort, 1851, vol. i. p. 285. 



Ann. S^^Ma^.N. Hist. Ser.2. Vol.xv. 30 



