REPORT ON THE LAMELLIBRANCHIATA. 43 



Jeffreys is the presence of a rather strongly marked impressed ray within the valves, 

 extending obliquely from beneath the umboues down the anterior side. 



Necera obesa, Loven. 



I^ecB-ra obesa, Lovdn, Ofversigt k. Vetensk.-Akad. Forhandl., 1840, p. 202, Xo. 326. 

 Necera obesa, Sars, Moll. Arct. Xorv., p. 86, pi. vi. figs. 4a-c. 

 Netera pelliicida, Stimpson, Invert. Grand Manan, p. 21, pi. i. fig. 13. 



Habitat. — Station 78, off San Miguel, Azores, at a depth of 1000 fathoms, volcanic 

 mud (Challenger) ; West Norway, in 40 to 650 fathoms (Sars) ; Eastern North America 

 (Verrill); off* Long Island, in 40 fathoms (Stimpson). Atlantic Ocean, lat. 47° 38' N., 

 long. 12° 8' W., 2435 fathoms (Jeffreys, "Porcupine" Exped., 1869); also Stations 1 

 and 3 of the 1870 Expedition; lat. 48° 38' N., long. 10° 15' AV., 567 fathoms; lat. 

 48° 31' N., long. 10° 3' W., 690 fathoms. 



A single small right valve from the above Station, only 5 mm. in length, is all that 

 was obtained of this species. In form and sculpture it corresponds precisely with the 

 above quoted figure of Sars. 



Necsra meridionalis, n. sp. (PL IX. figs. 6-66). 



Testa fragilis, tenuissima, alba, concentrice subrugose striata, epidermide tenui induta, 

 paulo in^quilateralis, alta, antice late rotundata, postice breviter lateque rostrata. Valvae 

 fere asquales, subtumidaa, sinistra sulco hand profundo ab umbone radianti prope 

 extremitatem posticam sculpta. Margo dorsi anticus brevis, primo parum obliquus, 

 aliquanto arcuatus, posticus horizontalis, fere rectus ; margo inferior late curvatus, antice 

 subito ascendens, posterius oblique surrectus, leviter sinuatus. Fossa ligamenti minima, 

 obliqua. Pagina interna nitida, radiatim substriata, dense minuteque granulata. 



This is a broadly rostrate species, excessively thin, high, tumid, broadly rounded in 

 front and somewhat obtusely wedge-shaped behind. It is white, covered with a very 

 thin epidermis, and exhibits distinct lines of growth and a shallow groove in the left valve, 

 radiating from the apex to the margin near the hinder extremity, there being only the 

 faintest indication of a similar furrow in the opposite valve. The dorsal margins are 

 very unequal. The anterior is short, faintly excurved at first, then arcuate and suddenly 

 descending, forming with the upcurved lower margin a broadly rounded extremity. The 

 posterior margin is much longer, almost horizontal and straight, and the ventral outline 

 is widely arcuate, except behind, where it rises with a faint incurvation in an oblique 

 dii-ection. The umbones are rather large and tumid. The cartilage-pit is very small, 

 inclined towards the posterior end, and the lateral lamellar tooth of the right valve is 

 elongate. The internal surface of the valves is somewhat 2;lossr, exhibits a sort of close 

 radiating substriation, and, under the microscope, appears to be minutely granular. 



