MOLLUSCA. 3 



sisting of two upper and two lower, are short ; the two external and upper ones are longer 

 and thicker ; and the two external and lower are of much greater length, strength, and thick- 

 ness. They are all provided with acetabula on the lower-surface. 



The name ellijjsoptera has been suggested by the curious oval fin which is developed at 

 the caudal extremity. The drawing which accompanies this description was taken from the 

 living animal, and is enlarged one-third of its natural dimensions. 

 Plate I. Fig. 1. Increased one-third larger than life. 



2. ARGONAUTA, Linn. 



Of the Argonauts captured during the voyage, we are enabled, with the assistance of 

 some specimens collected in the same seas by Mr. Cuming, to confirm the value of two very 

 excellent species, A. Mans and gondola described in 1817 by Mr. Dillwyn 1 but not figured ; 

 one subsequently named A. nitida by Lamarck, the other quoted by M. Deshayes as a variety 

 of A. tuberculosa. To these we have the pleasure of adding a third species, A. Owenii, 

 which has been satisfactorily determined by a comparison of the shells of each in different 

 stages of growth. The soft parts of A. Mans are figured in the beautiful work of De Ferussac 

 and D'Orbigny on the Cephalopods. 2 Of the A. gondola, Mr. Adams was fortunate enough 

 to preserve a young individual for some days alive, during which time he made a careful 

 drawing of it, including the development of the ovum. Living specimens were also taken 

 of the A. Owenii, and placed in spirits, but the liquid having escaped from the bottle through 

 some accident in the packing, the animals dried up and were found partially decomposed ; 

 the shells were preserved entire and form a characteristic series of different ages, agreeing 

 with one of adult growth in the collection of Mr. Cuming. 



1. Augonatjta GONDOLA. Arg. ccrrpore elongato-ovato, lateribus subcompresso, pallio aniplo punctis 

 grandibus vivide rufis ornato ; cajrite subangusto, brachiis tumidis breviusculis, acetabulis paucis, grandibus 

 confertiusculis rufo-marmoratis ; velamentis minute rufo-punctatis; iiifundibulo lato, breviuseulo, ad extre- 

 mitatem bifuxcatim tubuloso ; testa lateribus subplanulata, radiatim rugata, rugis subprominentibus, vix 

 undulatis, alternis brevioribus, medio descendentibus, superne dilatata, auriculis extrorsum valde prolongatis ; 

 carina latissima, fortiter tuberculata, tuberculis acute compressis; apertwd latissima, suboblongo-quadrata, 

 antice utrinque spiram canaliculata ; colore lactea, sordide fusco ad latera jilus miimsve tincto. A. gondola, 

 Dillwyn, Descriptive Catalogue of Shells, vol. i. p. 335. 



Hab. South Atlantic Ocean. 



The animal of A. gondola approaches nearer to the A. Mans figured by De Ferussac and 



D'Orbigny in the work already referred to ; from which the shell differs most remarkably by 



the outwardly prolonged growth of the auricles on each side of the spire. The keel is moreover 



wider with the tubercles rather distant and more compressed. The wrinkles are much 



less numerous than in A. tuberculosa, and do not fade into solitary warts as in that species. 



1 Catalogue of Shells, vol. i. p, 334-5. 2 Hist. Nat. Moll. 1834. pi. 5. 



