CIRRIPEDIA 



of the fixed tergum. This radius has a triangular shape, broad at its base and sloping towards 

 the upper extremity. 



The fixed tergum is irregularly rhombiform, or, more precisely as the basai margin though 

 narrow may not be overlooked, elongated pentagonal. Its apex is bluntly beaked. It consists of 

 three portions — a middle and two latéral. The middle portion is narrow, pointed at the apex 

 and increases in width towards the base ; it forms a kind of rim projecting over the surface of 

 the two latéral portions, which do not lie exactly in the same plane but describe together a very 

 obtuse angle. Thèse latéral portions are of nearly equal size and both ofa triangular form. 

 One is placed between the rim and the scutal margin with the occludent margin short and 

 slightly hollowed out ; the Unes of growth of this portion run parallel to the scutal margin. The 

 other portion fits in between the rim and the carina ; its occludent margin is longer and slightly 

 curved and its Unes of growth run parallel to its basai margin and the free edge of the carina. 



The rostrum and the carina though exhibiting by far their largest portions at the side of 

 the movables valves (Fig. i) form also part of the wall at the other side of the shell. Both valves 

 project freely — the carina more so than the rostrum — beyond the edge formed by the scutum 

 and the tergum. The projecting portion of the carina is distinctly recurved, whereas that of the 

 rostrum is nearly straight. The lines of growth of both valves are very distinct, they are 

 irregularly parallel to one another and to the basai margins of the valves. 



Both valves are furnished with a double articular ridge, separated from one another by 

 a distinct longitudinal furrow. They hâve in both valves about the same direction, running from 

 the base of the valve near the place where the rostrum meets the carina and vice versa towards 

 the apex. In the rostrum the upper of this double ridge forms the margin of the valve along the 

 base of the movable scutum ; in this valve the under extremities of both ridges project like teeth 

 fitting into excavations of the rostral margin of the carina. In the carina the double ridge is 

 separated from the slightly curved upper (or tergal) margin by a triangular portion, which is 

 rather broad where it meets the rostrum and terminâtes in a point at the apex of the valve. The 

 upper ridge of the rostrum terminâtes also in a tooth-like projection which fits into the exca- 

 vation between the two teeth of the cannai margin of the rostrum. 



Fig. 3 



Same animal seen from the side of the fixed scutum 

 and tergum and parti}- from underneath. Magni- 

 fied 4.4 diameters. 



The circumference of the shell, seen from underneath. 

 Magnified 10 diameters. s', f, c and r as in figure 2. 



