\I:.,ON MI\. 



K.-.milx III. AIK.ON A I Til 



I ARGONAUTA, Liim. 

 Tlir shells <>!' . I ri/niHI iiffl. a It lioilgl) Illllliei < HI-, -pecie- li:i\t I.een 



described, are nil referable 1<> three uToups. :in<l ma\ n<>- 



tliMt Dumber of distinct species. These type- are : 



1. That of A.hitniii. Kil>s few and distant, keel l.rond. 



Here belong, besides the t\pe. .1. Cminnli I'a rkiii-on . 

 rnniufa Conrad, dix/xir ( 1 oiir:i<l. tjnmlnlu Dillw.. Owenti 

 Adnins. jmliln Conrnd tnid K<x-li i<nui Dimker. 

 *2. Th;it of A. An/0. Uilis iiuincrmis. closer ; keel H:IIT<.\\. 



r |\> the tvpr species m:iy lu- added J. f,'rnnr ri Dimker. 

 rinii]irt'#*ii !>!.. wpansa Dall., Nouri/i Lorois. /'(ic/iirn 

 Pall., fragili* I'MrUinsmi and /xi/ti/r/o Coin-. 

 3. That of A. nodosa. Kil>s ntiinerous. fnhrmtldfcd, keel 



rather nai'row. 



Within each of these o-roups species have l>ceii formed upon 

 the presence or al.sence of lateral "auricular" extension- <M 

 hoi'ns of the edo-e of the aperture. Imt lar^e snite> of sjx'cinieiis 

 show that this character is by no means constant, and that it 



exists indeed, in all stages of development. Dr. K. von .Marien- 



who was the first to perceive this <rn>npinr and the non-specific 

 character of the horns, has proposed to designate under each 

 -pecies four forms, viz.: 



a. Forma mutica. Aperture narrow, lateral edo-es straight. 



6. Forma obtusangula. Ends of aperture margin t'orinin^ -in 

 alible with the plane of volution. 



c. Forma aurita. Ends of aperture margin produced into a 



spine at ri^ht angles to the plane of volution. 



d. Forma agglutinaus. Margin of aperture an^ulated at it- 



ends, hut the angles oppressed to tJie. tt/n'rr. 



The animal of the Argonaut-shell, supposed at first to In- 

 parasitic in it, has received the generic name of OnjUin,- -iveii 

 liy Leach as from Kalinesqiie. The Oci/f/m,' ,,f tlu- latter author, 

 however, was not intended ly him to apjly to the animal of the 

 Argonauta. At any rate the UryfJinr of I. cadi beCOUK 



* Ann. Ma u . N. Hist., xx, 3d ser., 1H67. 



