130 THE VOYAGE <>F If. M.S. CHALLENGER. 



margin. The hitter part is slightly concave. The apex is bluntly pointed. At the 

 under side the valve shows a distinct rim at both occludent margins; this rim slightly 

 increases in width towards the apex of the valve, where the two meet. 



The fixed scutum is shorter, but perhaps a little broader towards the base than 

 the fixed tergum. The shape of the valve is triangular, and being very broad and 

 convex at the base, and pointed, slightly beaked at the apex, it resembles half the 

 surface of a conns. The occludent margin is hollowed out for the reception of the 

 corresponding margin of the movable scutum; it forms the free edge of a separate and 

 inflected portion of the valve, which is extremely narrow upwards and distinctly widens 

 downwards. At the tergal margin a kind of radius is visible, which projects over the 

 free edge of the fixed tergum ; at the upper half it is extremely narrow and hardly visible. 

 .it the under half, on the contrary, it forms a, rather broad and triangular portion. 

 The basal margin is very irregularly toothed. The umbo is at the apex ; the valve 

 is added to at its inferior extremity. The lines of growth are distinct, but have a very 

 irregular course. 



The fixed toy inn has a very irregular shape ; it consists of three portions — a middle 

 and two lateral ones. The middle portion is very narrow at the apex, and increases 

 considerably in width towards the base. It projects very much over the surface of the 

 two lateral parts, hence may be considered as a kind of rim; it is curved, and projects 

 very much beyond the basal margins of the two lateral parts. The valve has two 

 occludent margins which meet at the apex. Of the lateral portions, one is placed 

 between the rim and the immovable scutum, and this is added to in a direction parallel 

 to the scutal margin ; it has an irregular triangular shape and a short occludent margin. 

 The other lateral portion is triangular also; it has a longer occludent margin at the edge 

 of a narrow part which is bent forward. Its basal margin is the margin with which 

 it touches the carina; the lines of growth of this valve are parallel to the latter margin. 

 The projecting middle part of the valve probably corresponds to the spur which is so 

 well-developed in most species of Balanus. When seen from the under side, the valve 

 consists of two parts, meeting in a line running longitudinally in the middle of the pro- 

 jecting middle portion. These two parts describe together a distinct angle. 



Rostrum and carina are both triangular in outline. The rostrum is more convex 

 and a little more robust. Both valves have the umbones in their normal places. However, 

 in both they project freely beyond the edge formed by the scutum and tergum. This 

 projecting portion is larger in the carina than in the rostrum ; moreover, it is slightly 

 recurved in the former and curved inward in the latter. Both valves are furnished with 

 one very distinct and two rather shallow longitudinal furrows, and where the valves meet 

 cadi other, it is into these furrows that the well-developed teeth of the other valve pene- 

 trate. The lines of growth are rather distinct, and, though not very regular, they are 

 about perpendicular to the direction of these furrows. The number of teeth by which 



