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the head to the tail, when extended floating upon the surface of the 

 water, was 1 finches; sometimes one or two lines more or less. 

 The body of the animal is subcylindrical, terminating in a tail, which 

 gradually becomes more slender towards the extremity, until it 

 finally terminates in a delicate point. The head is short, with very 

 small conical tentacula in pairs ; two superior, and two inferior ; 

 three (and in G. octopterygius, Cuv., four) branchial fins on each 

 side, opposite, palmated, and digitated at their extremities; the num- 

 ber of digitations, however, varying; and the centre digitations are 

 the longest; the first branchial fins, those nearest the head, are 

 larger and denser than the others. The mouth is armed witli bony 

 jaws; the body is gelatinous and covered by a thin and extremely 

 sensible membrane. 



" These little animals were very delicate and fragile in their struc- 

 ture, and although many, indeed, I may say numbers, were caught, 

 yet very few in comparison were found to be in a perfect condition, 

 some being deficient in one, two, or more fins, and others being com- 

 pletely crushed. Not one of the specimens caught on this occasion, 

 or during the voyage, had the silvery line or streak running down 

 the back, from the head to the extremity of the tail ; branching oif 

 also to the fins and along the centre of each of the digitations. Seve- 

 ral Porpitce were also captured in the net at the same time with 

 these animals, and serve as food for them. 



" It caused much regret to see the change death produced in the 

 beauty of these interesting little animals, and all means of preserving 

 them were found to be useless. When placed in spirits, the digits 

 of the branchial fins speedily became retracted, the beautiful purple 

 gradually faded and at last disappeared, and the delicate pearly white 

 of the under surface of the body and fins peeled oif and disappeared; 

 thus did this beautiful moUusk become decomposed in less than the 

 space of an hour. Some moUusks quickly lose their colour after death, 

 but retain their form for a long time ; but these speedily change 

 after death, both in form and colour, and the beauty before so much 

 admired perishes never to be regained. 



" When taken in the hand, the under surface of the animal soon 

 becomes denuded of the beautiful pearly white it previously had, 

 and at that time appears like a small transparent bladder, in which 

 a number of air-bubbles are observed, together with the viscera. On 

 the abdomen being laid open, a large quantity of air-bubbles escaped, 

 and perhaps a query may arise how far they assist the animal in float- 

 ing upon the surface of the water ? 



" The figure of Glaucus hexapterygius in Cuvier's work ' Sur les 

 MoUusques,' is tolerably well executed, but no engraving can convey 

 to the beholder the inconceivable delicacy and beauty of this mollusk; 

 in the engraving alluded to, there is an inaccuracy at least as compared 

 with the specimens before me, — in the digitated processes of the fins 

 not being sufficiently united at the base ; in the living specimens 

 before me, they were united together at the base, and then branch- 

 ing off became gradually smaller until they terminated in a fine 

 point. Again, in the engraving in Cuvier's work, the anal orifice is 



