Tertiary.] PALEONTOLOGY OF VICTORIA. IMollusca. 



Plate VII., Figs. 1-4. 



VOLUTA MACROPTERA (McCot). 



Description. — Shell fusiform, until nearly adult, when the outer lip becomes 

 dilated into a very large thin-edg-ed, triang-ular flattened wing, the outer margin of 

 which is slightly convex, the posterior margin slightly concave, running up halfway 

 to the suture of the penultimate whorl in a slight channel ; the approximately rectan- 

 gular junction of the outer and posterior margins broadly rounded. Apical angle 

 about 55° in middle-aged specimens, and 35° in young ones 1^ inches long. Spire 

 with a concave outline of 4 rapidly enlarging whorls and a mammillary cap-shaped 

 pullus of IJ half-turns, the basal half-turn of the pullua less than half the width of 

 the next succeeding turn of the spire, the remaining turn nipple-shaped with a small 

 excentric projecting apex ; the length of the pullus equalling once and a half the width 

 of the next following turn of the spire ; turns of the spire embracing the preceding 

 one at the suture, near which they are concave, then forming a convex shoulder and 

 nearly parallel with the axis of the shell below ; body whorl fusiformly narrowed in 

 front and marked with a broad sigmoid siphonal notch, without anterior crest or 

 ridge. Inner lip excessively thin, moderately spreading; plaits of the columella, 4, 

 widely separated, very prominent, narrow, moderately oblique, the •} anterior nearly 

 equal, the posterior one smaller. Aperture moderately wide, oblong, narrowed above 

 and below, becoming effuse with age. Pullus smooth ; the next two turns of the 

 spire, with excessively fine spiral striae, only visible with the lens (about 10 or 11 in 

 the space of 1 line) ; rest of the spire and body whorl smooth or marked with fine 

 lines of growth. Length of pullus, 4 lines; width of ditto, 3 lines ; length of adult 

 (including the pullus, which is 3 lines), 6 inches ; proportional length of body whorl, 

 /g% ; length of wing, ^% ; width of body and wing, -^^^ ; width of body on inside 

 of base of aperture, -^jp^. 



There is no Kving or fossil species at all like tlie present, in the 

 large thin angular wing-shaped outer lip and fusiform body. 



Young specimens 1^ inches long are iiTegularly fusiform, of two 

 whorls in addition to the pullus of nearly two. 



The layer of shell bearing the microscopic spiral striae seems 

 very liable to fall off, leaving the whorls only marked by the lines 

 of gi'owth. 



Not uncommon in the passage beds of the Tertiary sands 

 (A* 22) at Bird Rock, near Geelong. 



Explanation op Figures. 

 Plate VII. — Fig. 1, back view of specimen, natural size, the tip broken. Fig. 2, front view 

 of portion of specimen, natural size, showing mammiUated apex of spii'e and adult form of 

 outer lip. Fig 3, front view, natural size, of specimen, showing the apex of spire and form of 

 plaits on the columella. Fig. 4, front view of very young specimen, natural size, showing 

 undilated outer lip, the folds on the piUax, and the mammillated apex of the spire as large as in 

 the adult. 



Feedekick McCoy. 



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