(sect, c), balanus pcecilus. 247 



specimens which I have seen, leads me to suspect that they 

 may have grown under unfavorable circumstances. This 

 species differs considerably in general aspect, but not much 

 in essential characters, from B. amphitrite ; the absence, 

 however, of an adductor ridge to the scutum, and the sharply 

 truncated spur of the tergum, are sufficient to distinguish 

 them. In the opercular valves this species comes near to 

 B. vinaceus, also from the west coast of South America; 

 but the striated scuta of that species, the cancellated inner 

 lamina of the parietes, the general colouring, and square 

 porose radii, are amply diagnostic characters. 



General Appearance. — Shell fragile, tubulo-conical, orifice large, 

 passing from diamond-shaped into oval. Colour fine dark rose, 

 freckled with transverse, sharply pointed, fine zig-zag white lines : the 

 pink is also so arranged as to obscurely give to the walls a longi- 

 tudinally striped appearance : radii generally rather whiter than the 

 walls, and similarly freckled : terga similarly freckled : scuta dull red, 

 with a white band along the scutal margin. Basal diameter of largest 

 specimen half an inch. 



Scutum, externally smooth : internally, articular ridge moderately 

 developed, slightly reflexed : there is no adductor ridge : there is a 

 distinct pit for the lateral depressor muscle. Tergum, with the scutal 

 margin unusually prominent, toothed : longitudinal furrow shallow, the 

 edges apparently having no tendency to fold in : spur short, barely one 

 third of width of valve, with the lower end sharply truncated, parallel 

 to the basal margin : articular ridge and crests for the depressores 

 moderately prominent. 



Compartments. — Walls very fragile, with the outer lamina not 

 thicker than the inner lamina. Radii fragile, broad, with their 

 summits moderately oblique ; their sutural edges have the septa 

 plainly denticulated on both sides, with the interspaces filled up 

 solidly nearly to the tips of the septa. Alee, with their summits 

 more oblique than those of the radii; their sutural edges smooth. 

 Basis with an underlying cancellated layer. Mouth : labrum with 

 three unusually large teeth on each side of the notch : mandibles with 

 the fourth tooth tolerably well developed, the fifth being confluent with 

 the inferior angle. Maxilla simple. Cirri, — first pair with one ramus 

 longer by about four segments than the other ramus, which has con- 

 siderably protuberant segments : second pair with segments only 

 moderately protuberant : sixth pair with segments much elongated, but 

 bearing only four pairs of spines. 



