from the Gulf of California, etc. 395 
laceis ornata; angulo postero-dorsali rectilineari; facie posteriori cordiformi, 
sub-biangulari; latere antico angustato, citò rotundato; margine ventrali denti- 
culato, postice pt intus alba vel flavescens, violaceo nubeculata, ad mar- 
ginem dorsalem fusc . 
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 isa little curved ; posterior end heart- 
Shaped, faintly biangular, the umbonal angle obtuse and rather ill 
defined, but the radiating striae 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 inc 
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, and the posterior basal termination protrudes more; the 
Stri:, too, are decidedly punctate along the anterior umbonal 
stope. Some small specimens are very broad 
especially near the anda 
LUCINA ORBELLA (Pl XV. Fig. 5.) 
Lucina orbella, Gould; Proc. B. S. N. H., Nov. 1851. IV. 90. 
T. parva, tenuicula, subglobosa, albida, concentric? inequaliter striata ; 
apicibus medianis, haud haud eminentibus, absque ue lunulà ‘antica; lateribus fero sym- 
