948 PELECYPOUA. \_Eulamellibranchia. 



"1. Tellina deltoidalis, Lamarck, 1818. Plate 59, tig. 11. 



Tellina deltoidalis, Lamarck, A.s.V., v, 1818, 532 ; Delessert, Recueil de Coq., 

 1841, No. 49, pi. 6, f. 7 ; Haiiley, Cat. Rec. Biv. Shells, 70, 347, pi. 13, 

 f. 3 ; Conch. Icon., xvii, 1866, pi. 7, f. 29 ; Romer, Conch. Cab., x, 1871, 

 54, pi. 15, f. 4-7 ; C.M.M., 67 ; M.N.Z.M., 143. T. lactea, Quoy and 

 Gaimard, Voy. Astrol., iii, 1835, 501. pi. 81. f. 14-16; Crit. List, 42; 

 Index, 91. 



Shell moderately large, fairly solid, ovate, yellowish-white, inequi- 

 lateral, strongly folded behind, the right valve slightly more convex 

 than the left. Beaks in front of the middle, contiguous, not raised, 

 broadly convex. Anterior end mostly shorter, convex, the dorsal 

 margin long, convex, slowly descending. Posterior end produced, 

 subangular. the dorsal margin long, straight or slightly concave, 

 descending, both valves folded and turned to the right ; basal margin 

 broadly rounded, a little sinuate at the middle. Sculpture consisting 

 of fine concentric striae, obsolete on the upper half of the valves, and 

 very faint close radiate striae. Epidermis very thin, horny, persistent 

 only near the margins. Colour white or yellowish-white, usually of 

 a deeper yellow towards the umbones. Interi r white, sometimes 

 stained with yellow or orange, porcellanous, radiately striated, dis- 

 tinctly so at the basal margin, and with 3 distinct posterior radial 

 ribs, crossing the muscle-scar. Hinge : Eight valve with 2 cardinals, 

 the posterior stouter and bifid, 1 rather large triangular lateral near 

 the cardinal, and 1 small posterior lateral distant from the cardinal ; 

 left valve with 2 narrow cardinals, and almost obsolete anterior and 

 posterior laterals. Ligament rather short, strong, inserted on well- 

 developed nymphs. Adductor-scars unequal, the anterior very high 

 a,nd narrow, the anterior irregularly rounded and smaller. Pallinl 

 sinus linguiform, extending to the anterior muscle-scar. 



Length, 36-5 mm. ; height, 30 mm. ; diameter, 12 mm. (type). 

 Length, 41 mm. : height. 33 mm. ; diameter, 14-5 mm. (T. lactea, 

 Q. & G.). Length, 73 mm. ; height, 53 mm. ; diameter, 22 rnm. 

 (Auckland specimen). Length, 46 mm. ; height, 33 mm. : diameter, 

 13mm. (Victoria specimen). 



Type in the Mus. Hist. Nat., Geneva. 



Hob. North and South Islands : Bay of Islands, Hauraki Gulf ; 

 Wellington Harbour ; Akaroa Harbour, in 6 fathoms (H. S.) ; Dun- 

 <;din Harbour. Kermadec Islands (Captain Bollons). Also Australia 

 and Tasmania. 



Remarks. The variations of this species in form are very con- 

 siderable, as already pointed out by Dr. E. Romer. The typical 

 form is rather small, and the beaks at the middle of the length. 

 Usually, however, the anterior end is slightly shorter than the pos- 

 terior. T. lactea, Q. & G.. is a more solid, highly triangularly ovate 

 form, with the beaks at the middle of the length and the hind dorsal 

 slope distinctly excavated. Specimens which exactly agree with the 

 figures in the Voy. Astrol. occur in Dunedin Harbour in stiff mud. 



