LEUCOZONIA. 151 



genus is not umbilicate, and the outer margin is of a different 

 character. 



Type. — Buccinum smaragdulum, Linnaeus. 



Leucozonia (Latirolagena) staminea, Tate. 



1888. Leucozonia staminea. Tate, Trans. Eoy. Soc. South Aust vol 5 



p. 163, pi. ix. fig. 13. 

 1893. Leucozonia staminea, Tate and Dennant, id. vol. xvii. pt. 1, p. 219. 



Shell bucciniform, globose, solid ; protoconch (Plate V. Figs. 8a-5) 

 composed of one and a half turns, the earlier portion being 

 exceedingly small, subsequently becoming large, much inflated and 

 oblique with reference to the axis of the shell, the later portion 

 is distinctly longitudinally costated, which ornament obtains to the 

 fracture denoting the commencement of the brephic stage of growth ; 

 whorls to the number of four, convex, slightly concave in the 

 neighbourhood of the suture posteriorly, and ornamented with 

 closely-set spiral lines, some of which are regularly and distantly 

 spaced and much more accentuated on the anterior half of the 

 body-whorl, smaller ones appearing between; lines of growth 

 conspicuous, causing minute granulations at the points of inter- 

 section with the spiral lineations ; aperture ovate, broad in front ; 

 outer margin sinuous, Urate within; columellar border smooth,' 

 excavated, carrying three slightly oblique plaits anteriorly, each 

 terminating with a compressed denticle ; canal short and broad. 



The costae on the anterior portion of the protoconch are very 

 remarkable, this characteristic not being perpetuated in later 

 stages of growth, and seeming to indicate that Latirolagena had its 

 origin in costate forms such as Latirus, or Faseiolaria. Turning to 

 living examples of the subgenus, we find in certain individuals 

 of L. leucozonalis, Lamarck, a persistent attempt to preserve and 

 even to accentuate the costate character referred to, the costa; 

 remaining even in later stages of growth. Typical examples 

 of that species, now living in the West Indies, and of its ally 

 L. mhodrata, Gray, found in the Bay of Montija, West Columbia, 

 closely resemble L. staminea. L. smaragdula, Linnjeus, of the 

 Philippines, is more globose, has a more profoundly excavated 

 columella, a shorter canal, and wider aperture than has the 

 last-mentioned fossil species. 



