(sect, b), balanus navictjla. 221 



12. Balanus cymbiformis. PL 3, fig. ha, hb. 



Parietes and basis not porose. Scutum and Tergum with 

 very small articular ridges. Tergum broad, almost equi- 

 lateral. 



Hab. — Attached to a Gorgonia, Tubicoreen, near Madras, (Dr. Johnston). 

 Hab. unknown, Mus. Cuming. 



General Appearance. — I have seen only two specimens, kindly sent 

 me by Dr. Johnston, and a single specimen in Mr. Cuming's collection. 

 In most points this species agrees with the two last species. The shell 

 (excepting the rostrum), and even the opercular valves in Mr. Cuming's 

 specimen were of a very fine purplish-red ; in the other specimens 

 they were feebly tinted purple. The parietes are strongly ribbed in- 

 ternally, and are not permeated by pores. The basal cup is not porose, 

 but its inner surface is ribbed in lines radiating from the centre, and in 

 both these respects this species differs from the two foregoing. The 

 Radii are rather narrow ; they are paler coloured than the parietes ; 

 they have their sutural edges plainly crenated. The alee have ex- 

 tremely oblique summits ; the narrow rim added during the diametric 

 growth of the shell is white, the rest of the sheath being, in Mr. Cuming's 

 specimen, finely coloured like the parietes. Basal diameter of the 

 longer axis of the largest specimen, *4 of an inch. 



Scutum, rather narrow, with the basi-tergal corner much rounded 

 off; externally the lines of grov. ii are little prominent. Internally, 

 the articular ridge is extremely little developed, and not at all reflexed; 

 there is no adductor ridge ; there is a minute pit for the lateral de- 

 pressor muscle, placed almost on the edge of the valve. The Tergum 

 is broad, forming (the spur being excepted) an almost equilateral tri- 

 angle. The articular ridge is remarkably little prominent, and placed 

 close to the scutal margin. The spur is nearly half as broad as the 

 valve, with its extremity or basal margin in one case obliquely trun- 

 cated, and in another case nearly square. 



Animal's body unknown. 



13. Balanus navictjla. PL 3, fig. 6 a — 6 d. 



Parietes and basis not porose : carino-lateral compart- 

 ments very narrow, and of nearly the same width from top to 

 bottom : radii with their sutural edges smooth. Scutum 

 externally striated longitudinally. 



Hab. — Attached to Gorgonise, Tubicoreen, Madras (associated witli B. cal- 

 ceolus), Dr. Johnston. Hab. unknown, Mus. Brit, and Darwin. 



