REPORT ON THE LAMELLIBRANCHIATA. 229 



Nucula unnjimyensis, Suiitli (I'l. XVIII. figs. \2-V2h). 



Niirvla itrgxaijensis, Smith, Ann. ami Mag. Nat. Hi.sl., 1880, .ser. .5, vol. vi. p. 320. 



Habitat. — Station 321, oli' Monte Video, at the moiitli of the Kio de La Plata, in 13 

 fathoms ; mud. 



In describing this species I followed Hauley, whose excellent monograph of the 

 Nuculidse I then consulted, in regarding the longer side anterior, and that towards which 

 the beaks incline posterior, which is the reverse of what has been done in the descriptions 

 in this Report. The six specimens obtained by the Challenger are adult, and show that 

 the species is constant in form and general facies. They are of the same olivaceous tint 

 as the type, but exhibit at intervals rather more distinctly a few darker concentric zones 

 where the valves are somewhat deeply furrowed at periods of arrested growth. 



Nucula reticulata, Jeffreys. 



Nucula reticulata, Jeffreys, Anu. and Mag. Nat. Hist., 187G, ser. 4, vol. xviii. p. 429. 

 Nucula reticulata, JefEreys, Proc. Zool. Soc. Loud., 1879, p. 583, pi. xlvi. fig. 7. 



Habitat. — Station 78, off' San Miguel, Azores, in 1000 fathoms; volcanic mud. 



It is on the authority of Dr. Gwyn Jeffreys, who has examined the few valves from 

 this locality, and referred to them in the latter of the above works, that I designate these 

 with this name, for I have not seen the types procured by the " Valorous " expedition. 

 They agree very fairly with his description, but are more angular in front than the 

 figure, of whicli the anterior margins do not slo^ic to " a rather sharp point." 



Nucula ^yrofundorum, n. sp. (PI. XVIII. figs. 13-1 3a). 



Testa rotuudata, paulo iuEequilateralis, modice convexa, pallide flavescens, uitida, 

 tenuissime radiatim substriata, ad apicem marginemque inferiorem versus Itevis. Linea 

 cardinis fortiuscula, dentibus undenis in valva dextra novenisque in sinistra instructa. 

 Pagina interna radiatim tenuissime lineata, margine externo minute lirato-dentieulato 

 circumdata. 



Length 3 mm., height 2^, diameter If. 



Habitat. — Station 24G, Mid North Pacific, in 2050 fathoms ; Globigerina ooze. 



This species is very like the Atlantic Nxicula reticulata, Jeffreys, but may, I think, 

 be separated. It is perhaps a little rounder, slightly more equilateral, and much more 

 finely striated, indeed, the striae should rather be described as hair-like whitish lines. 



