C0NCH0DERMA VIRGATA. 147 



and acuminated at both ends, or moderately developed 

 and slightly arched and blunt at both ends : lateral lobes 

 of the scuta broad : valves imperfectly calcified. 



Hub. — Muudaue : extremely common on ships' bottoms from all parts of 

 the world. Falkland Islands. Galapagos Islands, Pacific Ocean. Attached 

 to sea-weed, turtle and other objects. Often associated with Conchoderma 

 aurita, Lepas anatifera, L. Hillii, and L. anserifera. 



General Appearance, — Capitulum, flattened, gradually 

 blending into the peduncle; summit square, rarely ob- 

 tusely pointed. Membrane, thin. Valves, thin, small, 

 sometimes imperfectly calcified, very variable in shape and 

 in proportional length, and therefore, situated at variable 

 distances from each other, but always remote and im- 

 bedded in membrane. 



Scuta, trilobed, consisting of an upper and lower lobe 

 (the latter generally the broadest), united into a straight 

 flat disc, with a third lobe standing out from the middle 

 of the exterior margin, generally at an angle of from 

 50° to 70° (rarely at right angles) to the upper part, and 

 generally (but not always) bending a little inwards. The 

 shape of the lateral lobe varies from rounded oblong to an 

 equilateral triangle ; as it approaches this latter form, it 

 becomes much wider than the upper or lower lobes. In 

 one specimen, and only on one side, the scutum (fig. 2 d) 

 presented five points or projections. In some specimens, 

 the scuta are very imperfectly calcified, and consist of 

 several quite separate beads of calcareous matter of irre- 

 gular shape, held together by tough brown membrane. 



Terga, extremely variable in shape, placed at nearly 

 right angles to the scuta: beyond their carinal ends 

 (fig. 2 b), the capitulum presents two small prominences, 

 which are important as indicating the position of the 

 homologous, ear-like appendages in C. aurita* The 

 upper ends of the terga are imbedded in membrane, and 

 project freely like little horns for about one third of their 

 length : this free portion exactly answers to the pro- 



* These have also been observed bv Dr. Coates; see 'Journal of Acad. 

 Nat. Sci. Philadelphia,' vol.vi, p. 134,1829. 



