342 BALAN11XE. 



7. Tetraclita ccerulescens. PI. 11, fig. 4 a — 4>d. 



Lepas ccerulescens. Spongier. Slaivter af Selskabet, 1 Bind., 



1790.* 



Shell with the upper part tinged greenish-blue, longi- 

 tudinally ribbed : radii moderately wide, with their summits 

 oblique : scutum with a small adductor and extremely 

 prominent articular ridge, united tog etlier and so forming a 

 small sub-cylindrical cavity : tergum with the spur not joined 

 to the basi-scutal angle. 



Hah. — Philippine Archipelago, attached to Balanm tintinnabulum ; attached 

 to a ship's bottom, and to Balanus tintinnabulum, both from the Pacific Ocean ; 

 attached to a massive coral, and associated with T. vitiata, and therefore from 

 the tropical eastern seas; Mns. Brit., Cuming, Stutchbury. 



General Appearance. — Shell conical, sometimes depressed ; surface 

 with rather broad, smooth, longitudinal ridges; whitish, with the upper 

 part greenish-blue, sometimes very feebly tinted with pink; radii white, 

 or mottled with blueish-green, or with pink. When the outer lamina 

 of shell has been corroded, the uprllled parietal tubes, of a dull blueish- 

 gray colour, are exposed. The radii are moderately wide, with their 

 summits very oblique. In basal diameter, one specimen was 1*8, and 

 another 1*5 of an inch. 



Scuta, externally furrowed very slightly in a longitudinal direction, 

 causing the lines of growth to become a little sinuous. The valve is 

 strong and thick ; and the epidermis, when preserved, is hirsute with 

 spines. The articular ridge is extraordinarily prominent; it projects, as 

 measured from the external surface of the valve, to an amount equalling 

 half the width of the valve in its widest part. The adductor ridge is 

 very short, and is united to the bottom of the articular ridge, thus 

 forming a small, nearly cylindrical tube, which runs up to near the apex 

 of the valve. The inflected occludent margin is broad and coarsely 

 toothed. The crests for both depressor muscles are not very promi- 

 nent. When the scuta and terga are articulated together, owing to the 

 great projection of the articular ridge of the scutum, its upper part is 

 separated from the tergum (fig. 4 h), by a remarkably wide and deep, 



* The longitudinally folded walls, as described by Spengler, the blue colour, 

 the habitat, namely, associated with B. tintinnabulum from the East Indies, 

 and more especially the expression " Valvuhe operculi cardine dentato mobilis," 

 apparently referring to the highly prominent articular ridge of the scutum, 

 leave little doubt on my mind that I have rightly named the present species. 



