from the Gulf of California, etc. 393 
radiating strize, especially across the disk. Interior tinted (melon) 
yellow, spangled with shining dots ; siphonal sinus spatulate, veined 
with numerous diverging strie ; ligament pit deep and long; ante- 
rior lateral teeth approximate to beaks. 
ongitudinal, vertical, and transverse diameters two and three 
eighths, two and one eighth, and one and one fourth inches. 
From San Diego. Lieut, Green. 
Usually found about half this size ; the concentric lamellar strice 
are then conspicuous; but these become worn off, and the shell 
grows more irregular and coarse towards the margin ; the interior 
is faintly tinted yellow when young, but very richly so when old. 
It is closely allied to A. corrugatum, Sowb. 
MACTRA NASUTA. 
This Species, described in Proceedings Bost. Soc. Nat. Hist., Nov., 
1851, IV. 88, agrees so nearly with M. falcata, also described 
by me, (op. cit. III. 216,) that I hesitate to reproduce it as new with- 
out a direct comparison of the two shells, which I have it not now in 
my power to make. They will for the present, therefore, be 
regarded as synonymous. M. falcata, however, was found at 
Puget’s Sound, while M. nasuta was found by Maj. Rich at San 
Pedro, and by Lieut. Green, (with a doubt,) at Mazatlan. 
MACTRA MENDICA (Pl. XV. Fig. 4.) 
Mactra mendica, Gould ; Proc. B. S. N. H., Nov. 1851. IV. 88. 
: T. ovato-triangularis, compressa, solida, concentricé striata, epidermide ra 
induta ; apicibus antemedianis, acutis, incurvatis, margine dorsali utrinque citò 
declivi ; latere antico acnt® rotun ato; latere postico triangulari, de -V380 
angusté cordiformi, fortiter striato : intus lactea ; sinu siphonali, parvulo; fovea 
'amentali retrorsüm profunda, dente V-formi parvo; dentibus lateralibus con- 
Spicuis, 
Shell ovate triangular, small, solid, faintly striated concentrically, 
and coated with a pale fawn colored epidermis ; beaks antemedian, 
acute, incurved, dorsal slopes very steep, abrupt, anterior end rather 
acutely rounded; posterior end triangular, acute angled, with an 
= rupt ridge along the posterior umbonal ridge, the enclosed poste- 
riot area is narrow heart-shaped, more coarsely striate, with the 
lips a little protuberant. Interior milk white ; a very slight siphonal 
JOURNAL B. s. N. H. el OCTOBER, 1853. 
