THE SESSILE BARNACLES. 251 



a". Inflected occludent margin of the scutum broad, with four or five very coarse 

 teeth. Scutum white with purplish clouds and stains, the crests at base 

 strongly developed. Spur of the tergum tapering to a narrow end. Sheath 



somewhat purplish T. s. japonica 



fl'. Inflected occludent margin of scutum having rather small and close oblique 



teeth (one to every second growth-ridge of the exterior), their number de- 



jiending upon the degree of erosion of the valve, 



h^. Exterior and sheath, pink ; scutum, pinkish or white within ; tergum with 



tlie liasocarinal angle very prominent, the basal margin nearly at right 



angles with the carinal edge of the rather narrow spur T. s. rufotincta 



b\ Exterior usually dark, the sheath generally of a greenish shade. Scutum 

 dusky bluish-green, with narrow, multidentate, occludent border; crests 



in the base weak, Tergum narrow T. squamosa squamosa 



b". Exterior nearly white, gray, or blackish ; sheath blackish. Scutum wide, 

 vit)let-black and white, with strong crests for the depressor muscles. 

 c\ Pores of the wall rather coarse and not extremely numerous ; tergum 

 about half as wide as long, with the spur wide at the end, 



T. s. stalactifera 



c^ Similar, but tergum narrower T. s. stalactifera form confinis 



c'. Pores of the very thick wall small and very numerous. 

 (Z\ Width of tergum decidedly less than half its length — T. s. panamensis 

 d\ Tergum as in T. s. stalactifera; scutum white with a purple stain 

 on tergal margin T. s. mUleporosa 



TETRACLITA SQUAMOSA SQUAMOSA (Bruguiere). 



I am using this name as synonymous with T. foro<sa var. virklis 

 Darwin, It is a rather low, spreading, circular barnacle when grow- 

 ing on a flat surface, the orifice small, sutures obliterated or nearly so, 

 the outer lamina of the wall dark colored or gray, eroded, exposing the 

 filling of the parietal tubes, producing fine, more or less interrupted 

 ridges, which are usually headed -finely. The wall is thick, pores very 

 numerous and small. The sheath usually has a decidedly greenish 

 hue. The radii are represented by very irregular or vermiculute 

 crenulations on the flat radial faces. 



The scutum is dushy hliiish-green^ fading on the crest of adductor 

 ridge and toward the basitergal border. Articular ridge and furrow 

 small, in comparison with the West Indian subspecies. Adductor 

 ridge ver}"^ long, extending nearly to the apex and to the base, not con- 

 fluent with the articular ridge. Infexed occludent border narrow, set 

 with many small teeth. Crests for the lateral depressor muscle simple ; 

 the crests on the occludent side of the base very weak or wanting. 



Tergum very narrow, the basal margin sloping toward and nearly 

 in line with the carinal border of the spur. Spur narrow and long, 

 with the end rounded or pointed. 



This seems to be a very distinct form. I have seen a large number 

 without any tendency whatever to grade into either the Japanese or 

 the East African subspecies. Unfortunately, I have not been able to 

 compare the Tetraclitas of the squamosa group inhabiting India or 

 those of Australia. 



