314 PROCEEDINGS OF THE NATIONAL MUSEUM vol.xxiii. 



MACOMA (MACOMA) PHENAX new species. 



Shell small, thin and fragile, polished, l)luish white, siibequilateral, 

 very feebly ilexed Ijehind; beaks very low; dorsal margins declining 

 about equally before and behind the umbo; anterior end evenly 

 rounded, posterior end obtuseh^ pointed, base nearlv straight; hinge 

 normal, very delicate, the teeth minute; pallial sinus long and low, 

 subequal in the two valves, not reaching the anterior adductor scar. 

 Lon. 14, alt. 8, diam. 3.5 mm. 



Types from an artilicial pond screened from the sea so that onh^ 

 embr3"os could enter, occupied for researches on the development of 

 Ostrea virginica by the late Prof. John A. Ryder, at Jerome Creek, 

 Chesapeake Ba}', Virginia. The pond was made in February, 1884, 

 and these shells were found in the mud cleaned out of it in May, 1885, 

 so that they were, though fully adult, only 15 months old, or less. 

 Young shells of the same species were collected hy Stearns at the 

 mouth of the Hillsl)oro River, Tampa Bay, Florida. 



These specimens externally bear such a close resemblance to a some- 

 what stunted and obtuse TcUhui {Angulus) tenera Say, that, without 

 special scrutiny, they were identified as that species, and so remained 

 more than fourteen years in the collection. Desiring to examine the 

 hinge of Telllna tenera one day, a specimen of this lot was selected, 

 when, to my surprise I found the hinge to be that of JSLacoma. A care- 

 ful examination of all the specimens labeled TeU'ina tenera was then 

 made and another lot of half-grown shells from Florida were found 

 to be conspecilic. There is no sculpture except inconspicuous and 

 somewhat irregular lines of growth, and the exterior differs from 

 Trlh'na tenera chiefly in the more obtuse beaks and posterior end and 

 less marked flexure of the valves. 



Type.—y.o. 61719, U.S.N.M. 



MACOMA (MACOMA) MITCHELLI Dall. 

 (Plate II, figs. 4, 5.) 

 Macom<( mitchelH Dall, Nautilus, IX, July, 1895, p. 33. 



An illustration is now provided of this hitherto unfigured species. 



MACOMA (PSAMMACOMA) EXTENUATA new species. 



(Plate II, fig. 7.) 



Shell small, thin, white, with a yellowish flush on the disk near the 

 umbones; elongated, the anterior end slightly longer, rounded, poste- 

 rior end more attenuated, tiexuous. bluntly pointed; surface nearly 

 smooth, not polished, sculptured only with more or less obvious incre- 

 mental lines; hinge delicate, interior whitish, the pallial sinus long, 

 but not reaching the anterior adductor scar, largely confluent below. 

 Lon. 14, alt. 6.75. diam. 2.5 mm. 



