794 MESSRS. MELVILL AND STANDEN ON [Nov. 13^ 



tudincdibus circa 28, tmdique ctim insterstitiis, jnolchre 

 squamose cancellatis, margine dorsali recto ; %mnhonih')is 

 distantihus, patoUum inciorvis, margine ventrali apud medmin 

 sinuato, crenulato : cardine tdrinque midti-denticulato ; pagiva 

 interna alba. 

 Alt. 2-50, lat. 5, diarn. 275 mm. 



Hah. Persian Gulf : Gulf of Oman. Lat. 24° 58' X., long. 56° 

 54' E. ; 156 fathoms, shell-sand. 



A very small, abyssal, and probably almost if not quite adult 

 Area., almost precisely a miniature replica of A. noes L. or its 

 corresponding tropical ally. The form is narrowly trapezoid, 

 posteriorly somewhat expanded, the most conspicvious feature 

 being the marked longitudinal depression just below the umbones, 

 beyond which, anteriorly, the form is somewhat abbreviated. All 

 the examples we have seen are half -valves only. 



Arca (Bathyarca) anaclima* Melvill, sp. n. (Plate LIV. 

 fig. 6.) 



A. testa minuta, tenui, albo-lactea, oblique truncatula, tumida, 

 inoiquilateixcU, concentrice, simul ac radiatim, imdique liris 

 teiiitissimis circttvicincta et canceUata, latere antico oblique 

 arcuato, postice magis recto, margine ventrali leniter rotundato: 

 timbooiibtos promimdis, area dorsali angusta ; p>agina interna 

 alba, subpellucenie ; dentibits minutis, inconspicuis, iitrinque 

 a medio diver gentibus. 

 Alt. 2-50, lat. 3, diam. 2-25 mm. 



Hab. Persian Gulf: Gulf of Oman. Lat. 24° 58' N.. long. 

 56° 54' E. ; 156 fathoms, abundant. Lat. 25° 10' K., long. 60° 

 34' E. ; 40 fathoms, rarely. 



This little species, of which there were multitudinous examples 

 dredged, but all in dissociated valves, has as its nearest ally 

 Scapharca inceqidsculpta E. A. Sm., from Culebra Island, West 

 Indies, 390 fathoms, collected in Pteropod ooze by the ' Challenger ' 

 Expedition t. It is probably, according to Dr. W. H. Dall, who 

 has kindly examined specimens, hardly adult, but abundantly 

 difii"ers from other species inhabiting the same region. The 

 radiating and concentric cancellations are very beautiful, when 

 examined with a lens of moderate power. 



Arca (Scapharca) birleyana Melvill, sp. n. (Plate LTIL 

 fig. 8.) 



A. testa ovato-trapezoidea, solidula, sordide albo-cinerea, epider- 

 mide setosa ad latera prcecipue tecta ; valva sinistra dextram 

 patdlum siqyerimpendente, ad regionem umbonalem planato- 

 compressa ; umbonibus ip)sis 2}(i')~vis, latere antico abbreviato,. 

 p)Ostico recti-qtiadrato, margine dorsali recto, ventrali ad lat%i,s 



* r-vaKkiua, ^ sloping forward, obliquitj', from the form. 



f Report ' Cliallenger ' Exped., Zoology, vol. xiii. p. 267, pi, xvii. figs. 8, 8rt, 



