110 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



slightly, so that they are easily broken away. The two small 1-lobed 

 or square apertures are near together on the part of the body oppo- 

 site the area of attachment and are slightly prominent. The colony 

 contains individuals of various sizes and ages; from very immature 

 and minute ones up to those having a diameter of 3 mm. to 4 mm. 

 In some parts of the colonies the individuals are quite crowded, so 

 that their form is more or less modified by the pressure of the adja- 

 cent ones, but the connection between them, especially in the case 

 of the larger ones, is but slight and is by means of slender root-like 

 processes of the ventral region in which small vessels run. Test 

 thin, parchment-like and slightly translucent, its surface somewhat 

 rough and thinly incrusted with sand in the larger individuals. 

 Its color is yellowish, sometimes tinged with purplish brown about 

 the apertures. 



Mantle thin, adherent to the test, its musculature not greatly de- 

 veloped. Transverse and longitudinal fibers are numerous but are 

 not for the most part gathered into bands. 



Tentacles apparently normally 16, of two sizes placed alternately. 



Dorsal tubercle small; oval with its long diameter transverse to 

 the body axis. Its orifice is a straight or slightly curved slit like- 

 wise transverse to the body axis. 



Dorsal lamina plain-edged. 



First fold of the branchial sac well developed on each side of the 

 body, especially on the right side. On the left side it is more promi- 

 nent in the posterior region. One or two additional rudimentary or 

 vestigial folds, indicated chiefly or entirely by a somewhat closer 

 grouping of the internal longitudinal vessels, are recognizable in 

 large zooids, showing more distinctly on the right than on the left side 

 of the body. The scheme of the internal longitudinal vessels was 

 found as follows in a large zooid : 



Right side: dorsal 5 (25) 4 (5) 6 (7) 8 ventral. 

 Left side: dorsal 4 (23) 5 (4) 10 ventral. 



Internal longitudinal vessels closely placed especially on the large 

 folds; even on the intervals they are separated only by the width 

 of two stigmata or even less. The stigmata are rather wide. Trans- 

 verse vessels of two (in some places three) sizes, the smallest cross- 

 ing without interrupting the stigmata. 



Stomach short and wide with numerous (in large zooids about 30) 

 narrow longitudinal folds in its walls, and a rather long but slender 

 curved pyloric caecum. Intestine forming a rather compact rounded 

 loop; rectum moderately long, the intestine making a considerable 

 bend where the rectum commences. Margin of anus smooth with a 

 thickened border. 



Ovaries few (about five to seven) situated on the right side along 

 and close to the posterior part of the endostyle. They are small 



