1894, 



PROCEEDINGS OF THE NATIONAL MUSEUM. 723 



gularity of the shell arises; teeth strong, forameu large, incomplete, 

 the deltidia almost linear, but long; dental buttresses strong, receding 

 as they approach the arch of the valve; brachial valve flatter; teeth 

 strong, with very oblique buttresses; brachidium four-fifteenths the 

 length of the valve, barely one-third as wide as the valve, slender, with 

 a single spine at the point of recurvation, and a slight thickening, but 

 no sej)tum, at the cardinal apex; muscular impressions small and con- 

 fined to the upper fourth of the valve. Height of shell, 17; width, 12; 

 diameter, 9 mm. 



Station 3302, in 1,175 fathoms, mud; temperature, 36.8*^ F.; in the 

 Gulf of Panama. No. 122858, U.S.N.M. 



This species resembles Magellania ( Waldheimia) tvyvillei, Davidson, 

 but wants the septum and cardinal process of the brachial valve of that 

 species, which also has less oblique, shorter, and wider deltidia. It 

 has miich resemblance also to Macandrevia cranium, but is a more rec- 

 tangular, plump, and compact sliell, and appears not to reach the size 

 of 21. cranium. M. tenera has a shorter loop and more obvious septum 

 in the apex of the brachial valve. It is also a smaller species when 

 adult. 



MACANDREVIA DIAMANTIXA, new species. 

 Plate XXX, fig. 5; plate xxxii, figs. 3, 6. 



Shell smooth polished, dorso-v^ntrally compressed, flexuous, of a 

 rounded lozenge or " diamond "-shaped outline ; surface with faint in- 

 cremental lines, but no radial sculpture, waxen white; pedicle valve sub- 

 pentagonal, widest nearthe middle, theconvergingsides below produced, 

 the basal margin concave; beak short, wide, the foramen incomplete 

 below, with well-developed deltidia on each side; teeth strong, su]iported 

 by wide buttresses, forming wide recesses on each side; muscular im- 

 pressions indistinct, situated in the upper third of the shell ; no median 

 septum exists in this valve. The genital glands are of a reddish brown 

 color, shining through the shell As two short parallel streaks on each side 

 of the adductor impressions; brachial valve wider than high, svith the 

 base flexuous ui^wai d ; teeth strong, with very oblique buttresses hidden 

 under the dental plates and forming small foveolae ; cardinal process 

 short, stout, prominent, but not produced into a septum; bracbidium 

 very slender, extending to the basal third of the valve, the transverse 

 limb at the bight of the loop being wider than any part of the lateral 

 limbs, the bight itself being, of course, narrower, as usual; there are 

 two or three spiuules at the recurvation; the genital glands in this 

 valve show as a single brown streak on each side of the attachment of 

 the adductors. It is, however, longer than the paired streaks of the 

 pedicle valve. Height of shell, 18; width, 17: diameter, 7 mm. 



Station 33(32, in 1,175 fathoms, mud; temperature, 36.8^ F.; in the 

 Gulf of Panama. No. 122860, U.S.N.M. 



This elegant little species recalls Liothyrina wyvUlei, Davidson, in 

 its form, though more lozenge-shaped and less sharj)ly flexuous. 



