TRANSACTIONS OF WAGNER 



888 



TERTIARY FAUNA OF FLORIDA 



of the hinge-plate is noteworthy. The genus was named by Dcshayes, but 

 defined by Adams, who selected the type. Not having access to that species, 

 the characters have been taken from H. Denisoniana H. Ads. It is an Indo- 

 Pacific genus. 



Subfamily ZENATIINiE. 



Genus ZEN ATI A Gra}', 1853. 



Type Z. acinaces Quoy and Gaim. (+ Z. si;hindica Gray). 

 Mctahola C. Mayer, 1867 ; same type. 



Shell inequilateral, thin, compressed, siliquiform, smooth, with a con- 

 spicuous epidermis; dorsal area obscure ; beaks inconspicuous, adjacent, very 

 anterior; lunular area encroaching on the inner dorsal margin, hardly visible 

 externally; pallial sinus very deep, gapes conspicuous, the valves hardly 

 touching, except at the hinge and on the ventral margin ; ligament lanceolate, 

 short, somewhat sunken, not set off by any shelly barrier from the pit ; chon- 

 drophore oblique, large, posteriorly depressed below the hinge-plate, resilium 

 homogeneous and continuous between the valves ; dental armature concen- 

 trated ; left cardinal large, with an obscure accessory lamella between it and 

 the ligament; a short, high anterior lateral parallel with the anterior arm of 

 the cardinal, above which descends the lunular area ; behind the ligament a 

 very small, narrow posterior lateral (often lost) lies adjacent to the dorsal 

 margin ; valves below the cardinals reinforced by an obscure, thickened ray 

 of shell-substance, but which does not support the chondrophore ; upon this 

 ray, behind the adductors and below the ventral sinus of the cardinal, are the 

 scars of the pedal retractors ; right valve with the cardinal wide, hardly coales- 

 cent above, with two very small posterior but no anterior lamin?e ; both the 

 cardinals are wholly exterior to the pit. 



The species of this genus are confined to New Zealand. The above 

 description is taken from Z. DcsJiayesii Reeve [Lutrmia solcnoidcs Desh. non 

 Lam. -f- L. acinaces Rve. non Quoy and Gaimard). Tiie type of the genus 

 (Z. acinaces Quoy and Gaim., 1834 + Z. zelandica Gray, 1837 + L. 

 Cumingiana Desh., 1854) differs from Z. Desliayesii by the total absence of 

 lateral teeth or laminae, but these are so feeble when present, even in the 

 large Z. Desliayesii, that it would seem inadvisable to divide the genus, even 

 sectionally, on that account. The lunular area is obsolete in Z. acinaces. 

 The siphons are naked and wholly united, the gills continuous, and the 

 mantle edges united behind the foot in this genus. 



