118 



nut-brown on the umbones, rayed with green, more 

 conspicuous iu young specimens; in old ones the 

 dark chestnut-brown covers the whole and conceals 

 the rays; surface smooth and shining; within white, 

 iridescent; cardinal troth broad, prominent, and ob- 

 liquely flattened; lateral teeth broad, elevated, and 

 terminating abruptly posteriorly; muscular impres- 

 sions large; cavity of the' beaks unusually lame. 



SYN0N1 Ml>. 



I". (ARiiliM, liaf. Ann. gen. des Sc. Phys., vol. v. p. 32, |>l 



Ixxx. tigs. 16, IT, 1~. 19. 

 U. vkntkicosi *, Jiamcu. Silliman's Journal, vol. vi. p. J<>7, pi. 



13, fig. 1 I, a. h, c. 

 U. ovatub, Var. 6. I.nm. Vn. aans Vert., vol. v. p. 7f». 

 I. mi [dens, Lea. Trans. Amer. Philos. So< ., ii< w series, vol. 



in. p. 4W, pi. v. 



< IBSERVATH >NS 



I have in part copied Barnes' description. This 

 naturalist, Mr. Say observe-, "tirst distinguished the 

 species from U. ovatus, nob., to which it is v rv 

 closely allied, and appears to be absolute!) connect- 

 ed by a gradual transition of intermediate varieties. 

 The most striking difference appears to b< the more 

 depressed anterior [posterior] slope ol the ovatus. 

 Some old specimens and varieties an transversely 

 more elongated, as i- repr< scnted in Barm s 1 figure r. 

 The colour also is more <t less yellow, radiated with 

 green, or tinged with reddish-brown, parti< ularly on 

 the umbo, and sometimes extending over the whole 

 surface, almost obliterating the rays. On the inner 

 anterior [posterior] side, some Bpe< miens are beauti- 



