REPORT ON THE LAMELLIBRANCHIATA. 117 



Tapes {Amygdala) exalbida (Chemnitz). 



Venus exalbida, Chemnitz, Conch. Cab., vol. xi. p. 225, pi. ccii. fig. 1974. 

 Vetiiis exallmla, Sowerby, Thesaurus, vol. ii. pi. clxi. fig. 193. 

 Venus exalbida. Reeve, Conch. Icon., vol. xiv. fig. 13. 

 Chione exalbida, Deshayes, Cat. Conchif. Brit. Mus., p. 154. 



Habitat. — Station 316, off the east side of the Falkland Islands, in 4 to 5 fathoms ; 

 mud. 



This species is also quoted as coming from the Strait of Magellan by Sowerby and 

 Eeeve. It attains a large size, measuring at times as much as 110 mm. in length. Young 

 shells are more squarely truncate posteriorly than full-grown examples, which become 

 almost suhrostrate at the extremity. The form of the luuule also alters from roundly 

 cordate in the young to broad lanceolate in the adult. Romer places this species in his 

 section of Venus which he has named Katelysia. 



Subfamily Venerin^. 

 Venus, Linne. 



Venus philomela, n. sp. (PI. II. figs. 7-76). 



Testa ovata, in8ec|uilateralis, antice brevioi", alba, versus umbones interdum purpureo- 

 roseo tincta, concentrice tenuiter lirata. Lunula anguste cordata, linea impressa circum- 

 scripta. Umbones parvi, parum prominentes, ad apicem Iseves. Cardo dentibus tribus 

 in utraque valva instructus, in dextra postremo, in sinistra mediano bifido. Margo 

 valvarum intus minute denticulatus. Imprcssiones musculares irregulariter ovata?, 

 anteriori paulo angustiori. Sinus palUi par\ais, brevis, triangularis. 



This shell is of a transversely ovate form, narrower in front than behind, moderately 

 thick and decidedly inequilateral, the apex of the beaks being situated at a point marking 

 ofi' three sevenths of the entire length of the shell from the anterior end. The latter narrows 

 to a somcAvhat sharply rounded extremity. The front dorsal slope is very oblique, rather 

 rectilinear at first, then gradually curving into the arcuate end. The posterior dorsal 

 margin is almost horizontal, nearly straight for some distance until it commences to 

 descend and curve, forming the broadly rounded lateral margin. The ventral outline is 

 widely arcuate, curving up equally at both ends. 



The umbones are small, smooth, glossy, incurved and directed anteriorly. The 

 lunule is rather narrow, striated by the fine terminations of the concentric ridges which 

 are interrupted by a distinct impressed line or stria which limits the lunule. There is 

 scarcely any posterior dorsal area, it being very narrow, linear, nud not defined. The 

 hinge consists of three diverging teeth in each valve. Those of the right are unequal, 

 the front one being smallest, lamellar, subparallel with the margin of the valve, the 



