Zoohg!/.'\ NATURAL HISTORY OF VICTORIA. IMollusca. 



Plates 61 and 62. 



ARGONAUTA ORYZATA (Meusch.). 



The Tuberculated Argonaut, or Paper-Nautilus. 



[Genus ARGONAUTA (Lin.) = OCYTHOE (Rafinesque). (Sub-kingd. Mollusca. Class 

 Cephalopoda. Order Acetabulifera. Sub-order Octopoda. Family Argonautidae.) 



Gen. Char. — Three anterior or inferior pairs of arms subulate, gradually tapering from base 

 to apex. Superior or posterior pair forming two very broad expansions, by the recurving of the 

 terminal portion backwards in a broad curve, connected by a thick flat expansion with the 

 middle portion ; the two rows of suckers, like those of the other arms, bordering the edge. Two 

 rows of large cylindrical or sub-pedunculated suckers on each arm ; a broad membranous keel 

 on back of lower and upper pairs of arms ; the two middle pairs not keeled. Two aquiferous 

 openings at upper posterior edge of eye. Ears small, behind the eyes, under the cervical band. 

 A projecting button on inside of mantle fits in a groove at base of funnel on each side. Cervical 

 band moderate. Eyes very large, globose, covered by the colored skin of the body, except over 

 the pupil. Shell very thin, white, flexible when wet, equilateral, spirally involute in one plane, 

 radiatingly plicated or tuberculated on the flattened sides, with a bicariuate, shallow channel on 

 the narrow periphery ; aperture very wide behind, triangular ; no chambers or septa. Nucleus 

 Tery large, hemispherical.] 



Description. — Female: — body ovoid, convex in front, concave behind, obtusely 

 pointed below. Arms : — three anterior pairs long- and slender ; 1st longest, 2nd, 3rd, 

 and 4th* successively shorter, measuring from mouth between the rows of suckers to 

 the tip ; 1st or posterior dilated pair strongly keeled on back, with a broad mem- 

 branous web; suckers of outer row longer than those of inner row; 2nd and 3rd 

 pairs of arms not keeled, simply rounded on backf; 4th or anterior pair, with a very 

 prominent membranous keel on back. Color : whole skin of surface thin, with 

 close-set minute round spots forming purple circular clusters (about 2 or 3 in a space 

 of 3 lines) as big as a small pin's head, with paler and smaller dots between. Beaks 

 black, not compressed. The inside of the palmated expansion of the 1st or posterior 

 pair of arms is whitish without the chromatic, or color glands, of the general outer 

 surface. 



About 80 pairs of suckers on the large palmated arm, but becoming- very small 

 and alternate so as to look like one irregular line towards the recurved extremity. 

 About 75 pairs on 2nd arm ; about 64 pairs on 3rd arm ; about 80 pairs on 4th or 

 anterior arm. The suckers towards the thread-like tip of each arm almost too small 

 to count, but a little over 2 lines in diameter at base, elevated on thick cylindrical 

 peduncles of about the same diameter as the discs. The outer row of suckers on 

 each palmated arm long-er than those of inner row, and connected with each other 

 by a slight web; rows on the other arms equal. The anterior (or 4th) pair of arms 

 are connected together at base by a web about 4 lines high crossing over the funnel, 

 and they have an extension of the membranous keel of the outer mid-line, forming' 

 at the base a triangular, vertical, suspensory ligament for the funnel on each side. 



* Dr. Gray states the order of their length as 1, 2, 4, 3. 



t Ur. Gray, in his Cephalopoda Antepedia, page 32, says " the 2nd and 3rd pairs keeled on the outer side," I suppose 

 by mistake, as they are destitute of the prominent keel of the 1st and 4th pairs, and are simply rounded. 



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