122 BULLETIN OF THE 



oblique and very much more slender ; there are usually only five or six at each 

 extremity of the hinge-line, and the middle part is either quite edentulous or 

 only lightly irregularly granulous. A. glomerula measures as follows : Ion. 

 5.75 ; alt. 5.0 ; diam. 5.0 ; Ion. of hinge-line, 4.25 mm. A specimen of A. pec- 

 tunculoides measures: Ion. 7.75; alt. 7.5; diam. 5.5 ; Ion. of hinge-line, 6.25 mm. 



Barbados, 100 fins.; Bache, April 22, 1872, lat. 21° 14', 100 fms.; Station 20, 

 220 fms.; Station 19, 310 fms.; Sigsbee, off Havana, 450-480 fms. 



Considering the great variability of abyssal shells it is possible this may 

 eventually rank only as a variety of A. pectunculoides, but with the material at 

 hand I cannot see the way clear to unite them at present. 



Area polycyma n. a. 



Shell small, rounded quadrangular, slightly inequilateral, nearly equivalve, 

 moderately evenly inflated, whitish, with little or very fugacious epidermis ; 

 sculpture very remarkable, consisting, first, of very even, broad, rounded, regu- 

 lar, concentric waves (twelve or thirteen in number), separated by sharp, deep 

 grooves. In dead or worn shells these waves are smooth, or nearly so, but in 

 perfectly fresh (and especially young) shells on the surface of the broad slightly 

 flattened waves may be seen what look like two rows of subcylindrical, slightly 

 irregular grains of sand, arranged side by side, with their longer axes radiating 

 from the beak ; these granules, if so they may be termed, are really hollow, 

 and are the thinnest possible bubbles of shelly matter which leave, when rubbed 

 off by any slight friction, a couple of zigzag slightly elevated lines where their 

 bases were fixed to the shell ; a very slight friction will obliterate this, and 

 then the shell will be nearly smooth. The hinge area in each valve is elon- 

 gated and narrow ; the narrow farrow for the ligament goes straight across to 

 the margin from the beak (which is nearly opposite the middle of the hinge- 

 line) instead of obliquely, as in the last-mentioned species. The anterior, pos- 

 terior, and basal margins are all evenly rounded, and the surface evenly 

 convex ; the beaks not at all prominent ; the margin is perfectly smooth ; the 

 interior is undulated to correspond with the exterior, though the shell is pretty 

 solid and thick in proportion to its size ; muscular impressions distinct ; binge 

 with seven to nine smooth teeth in advance of the ligamentary furrow and tin 

 or eleven behind it ; middle teeth vertical, small ; those at the angles of the 

 shell somewhat oblique and larger ; there is no marked gap in the middle of 

 the series, and the teeth are strong broad and not striated. Lon. 9.75 ; alt. 

 6.0 ; max. diam. 5.0; lon. of hinge-line, 6.0 mm. 



Barbados, 100 fins, 



This shell has a sculpture unlike any <>ther in the genua of which I can find 

 any description. It may be of a similar nature to the "granules" of Par 



but the "bubbles' 1 projeel much more from the surface and have a very differ- 

 ent aspect from the tubular or honeycomb-like surface of Porom\ia. 



