22 



laceis ornata; angulo postcro-dorsali rectilinear! ; facie posteriori cordiformi, 

 sub-biangulari ; latere antico angustato, citb rotundato ; margine ventrali denti- 

 culate, postice coarctato ; intus alba vel flavescens, violaceo nubeculata, ad mar- 

 ginem dorsalem fuscata. 



Shell solid, ovate triangular, ventricose, the surface faintly radi- 

 ate striate, more distinctly so posteriorly, and then as if varnished so 

 as to obliterate the furrows ; color bluish white, pale fawn color, or 

 rayed with these colors, and most specimens have one or more 

 bluish zones ; anterior dorsal slope rectilinear and nearly at a right 

 angle with the posterior, which is a little curved ; posterior end heart- 

 shaped, faintly biangular, the umbonal angle obtuse and rather ill 

 defined, but the radiating strise going to the posterior basal angle 

 more distinct than elsewhere : anterior end rather acutely rounded ; 

 a very slight constriction of the basal margin posteriorly gives the 

 anterior portion a somewhat pouched appearance. Teeth of the 

 hinge well developed. Interior white, inclining to yellow, with 

 violet clouds, especially within the pallial impression ; a marginal 

 blotch along each dorsal edge seems to be pretty constant. Basal 

 margin with very decided teeth about the middle, becoming gradu- 

 ally more delicate in each direction. 



Long. diam. nine tenths of an inch ; vertical diam. six tenths of 

 an inch ; transverse four tenths of an inch. 



Inhabits San Diego. Lieut. Green. 



In general characters, especially in striation and posterior area, 

 it is much like D. anatinum, but that shell is more decidedly acu- 

 minate anteriorly ; the angle at the apex is less nearly a right 

 angle, arid the posterior basal termination protrudes more ; the 

 strise, too, are decidedly punctate along the anterior umbonal 

 slope. Some small specimens are very broad proportionally. 

 Some have the anterior end nearly as acute as D. anatinum, but 

 none the posterior end so much abbreviated, so nearly vertical. 

 The coloration is quite various., and often is mingled with lilac, 

 especially near the edge. 



LUCINA ORBELLA (PI. XV. Fig. 3.) 

 Lucina orbella, Gould; Proc. B. S. N. H., Nov. 1851. IV. 90. 



T. parva, tenuicula, subglobosa, albida, concentrice inequaliter striata ; 

 apicibus medianis, haud eminentibus, absque lunula antica ; lateribus fere sym- 



