82 LEPAS ANSERIFERA. 



Filaments five or six on each side. 



Var. (dilatata, young) ; valves rather thin, finely fur- 

 rowed, often strongly pectinated ; scuta broad, with the 

 occludent margins much arched, making the space wide 

 between this margin and the ridge connecting the umbo 

 and the apex : carina often barbed. 



Common on ships' bottoms from the Mediterranean, West Indies, South 

 America, Mauritius, Coast of Africa and the East-Indian Archipelago. Cen- 

 tral Pacific Ocean. China Sea. Chusan. Sydney. Attached to pumice, 

 various species of fuci, Janthinse, Spirulse ; often associated with L. anatifera 

 and L. Ilillii, and, in a young state, with L.fascicularis. 



General Appearance. — Capitulum more or less elon- 

 gated relatively to its breadth ; in two specimens, with 

 scuta of equal width, one was longer than the other by 

 the whole of the occludent margin of the terga. Valves 

 white, thick, (in young specimens sometimes diaphanous 

 and thin,) closely approximate to each other; surfaces 

 furrowed to a very variable amount. Terga generally 

 more plainly furrowed than the scuta, of which the basal 

 portion is generally less furrowed than the upper part ; 

 ridges, often rough, generally much narrower than the 

 furrows : in half-grown specimens (var., dilatata of 

 Leach,) the ridges are frequently denticulated, and there 

 is even sometimes a row of bead-like teeth along the 

 basal margins of the scuta. The ridges vary much, 

 sometimes alternately wide and narrow ; in two speci- 

 mens of equal size, there were, in one, thirty- two ridges, 

 and in the other only eighteen, on the scutum. 



Scuta, with the occludent margin rounded and pro- 

 tuberant to a variable degree, but always leaving a 

 rather wide space between the margin, and the ridge 

 which rims from the umbo to the apex ; apex pointed. 

 Right-hand internal tooth considerably larger than that 

 on the left, which is often reduced to a mere ridge ; 

 internal basal rim thick, sometimes furrowed along its 

 upper edge, but of variable thickness, sometimes not 

 extending as far as the baso-carinal angle. Terga, some- 



