VO l889 n '] PROCEEDINGS OF THE NATIONAL MUSEUM. 259 



Lamellibrauchs, PI. xvm, Fig. 8) but proportionally higher; beaks 

 prominent, recurved, frequently eroded ; radiating sculpture of numer- 

 ous fine, rather distant, sharp threads, more crowded near the beaks, 

 broader and less sharp near the anterior and posterior basal margin, 

 not dichotoinous; concentric sculpture of narrow, rather short, discon- 

 tinuous and irregularly placed ripples, strongest and more irregular 

 near the base, more crowded and regular and much less prominent near 

 the beaks, sometimes altogether or nearly absent, especially in the 

 young; lunular region impressed but not circumscribed, rather short 

 and broad, with a shallow flexure just outside of it; escutcheon long, 

 narrow, obscure ; interior nacreous, polished, the basal margin closely, 

 deeply, and sharply fluted, at all ages; anterior tooth-line concavely 

 curved with nine teeth, all developed; posterior series con vexly mod- 

 erately curved with nineteen developed teeth rather conical and 

 sparsely set; fossette shaped like the operculum of Fusus, curved in 

 harmony with the dorsal margin, wholly internal ; maximum longitude 

 of adult 12.5; altitude 0; diameter 5.5; vertical of beaks from anterior 

 end 2.75 mm . Young shell, longitude 7.25 ; altitude, 5.5 ; diameter 3.5 mm . 



Hab. — Station 2754, east of Tobago, iu 880 fathoms, ooze ; tempera- 

 ture 37o.9 F. 



This elegant shell is quite noticeable for its thin and light character, 

 its continuous fine sharp radii, and its narrow though not flattened 

 form. The young are more triangular, smoother, and proportionally 

 more plump, some of them recalling at first sight the adult N~. Verrillii 

 Dall. The internal fluting is particularly marked and sharp and has 

 suggested the specific name. There is no species which closely resem- 

 bles this form, though it belongs to the group which contains j\\ crenu- 

 lata, cancellata, decussata, etc. 



Suborder ARCACEA. 



Family AKCID.E. 



Genus ARCA Linuc. 



Area jamaicensis Gincliu. 



Area barbata Limit''. 



The above species were collected at the Abmlhos Islands off the coast 

 of Brazil near Bahia. 



Area Nc-ae Linuo. 



Area reticulata Gniftlin. 



Area Adamsi Shnttleworth. 



The three preceding species were collected at Station 2758, 00 miles 

 southeast from Cape San Roque, Brazil, in 20 fathoms, shelly bottom, 

 about 410 miles south of the equator. A. reticulata and A. Adamsi were 

 also obtained at the Abrolhos Islands. 



