THE ASCIDIANS 243 



DISTOMA PULCHRA sp. nov. 

 (PI. XXX, figs, 24 and 25.) 



General character of the colony. — Composed of sheaf-like bunches 

 united by their basal ends only, each bunch containing from ten to 

 twenty large and long zooids, some of which are free at the anterior 

 end for rather more than the length of the thorax, the remainder being 

 embedded in the common test, which is present, however, in small 

 quantity between the bodies of the zooids. Height of the bunches 

 about 30 to 25 mm. ; thickness at the upper end, /. <?., in the portion 

 containing the thoraces, about I3 mm.; in the next thicker portion, 

 i. ^., that containing the abdomens, about 10 mm. ; of the constricted 

 portion immediately behind the thoraces, about 6 mm. Bunches quite 

 regular both in form and size, having much the appearance of sheaves 

 of ' club ' wheat, the thoraces corresponding to the heads of the wheat, 

 the constricted portion to the position of the band of the sheaf, and the 

 enlarged abdominal region to the butt of the sheaf. 



Color. — Anterior end transparent, wholly without pigment ; poste- 

 rior end pinkish yellow from the great amount of food matter contained 

 in the abdomens of the zooids, which show distinctly through the thin 

 layer of colorless test. 



Test. — Small in quantity, indeed in the posterior half of the bunches, 

 scarcely visible at first sight ; somewhat more abundant anteriorly, 

 especially where a few thoraces are united. Examination of ample 

 material might reveal some evidence that closely adhering, flattened, 

 stolonic masses of test are present. Ordinary test cells very abundant, 

 but no bladder cells, spicules, or nodules present. 



Zooids. — Maximum number in a bunch about twenty. Very closely 

 packed in the bunches, particularly at their posterior ends ; anterior 

 ends more or less free, most of them for only a small portion of the 

 thorax, but a few for considerably more than the thorax. Frequently 

 a small number — two or three — in a bunch united to nearly the end, 

 and together free from the rest of the bunch for a part or all of the 

 extent of the thorax. 



Entire length of body distinctly visible through the test. Thorax 

 not withdrawn from the test in preservation. Thorax and posterior 

 end of abdomen strikingly thicker than middle portion of body. Total 

 length 20 to 25 mm., equaling height of the bunches. Thorax about 

 7 mm. ; narrow neck-like portion of body, about S mm. ; thick portion 

 of abdomen about 10 mm., maximum thickness of thorax, including 

 test, about 4 mm. ; of abdomen about 3.5 mm. 



