W. G. Van Name — Bermuda Ascidians. 357 



Analytical Table of Bermuda species of Bidemnum, based on the 



character of the colony. 



A. — Massive and irregular, opaque, consistency firm. Surface 

 roughish ; apertures far apart and conspicuous. Spicules uniformly 

 and thickly distributed. Color reddish grey or buff, almost flesh 

 colored. B. solidum. 



B. — Moderately thick, opaque, gelatinous. Surface smooth and 

 glistening ; apei'tures inconspicuous. Spicules confined to a stratum 

 in the interior of the colony, invisible from above. Color rich 

 brown. B. savignii. 



C. — Very thin, incrusting, gelatinous; zooids visible through the 

 test. Surface smooth, apertures inconspicuous. Spicules irregu- 

 larly distributed. General color blackish and greyish, irregularly 

 mottled, varying in places according to the abundance of the white 

 spicules and of the black pigment in the test and on the zooids. 



B. atrocanum. 



D. — Massive, partly opaque, consistency moderately firm, surface 

 slightly rough ; apertures prominent. Spicules rather uniformly 

 distributed, only moderately numerous. Color greyish, becoming 

 black on parts of the upper surface. B. porites. 



E. — Thin, incrusting, transparent, gelatinous. Surface smooth ; 

 zooids visible. Spicules in interior parts of the colony, not numer- 

 ous enough to greatly diminish the transparency of the colony. 

 Little or no dark pigment. B. lucidum. 



F. — Thin, incrusting, translucent. Surface smooth, zooids more 

 or less concealed by the abundance of spicules, which are so dis- 

 tributed that the surface of the colony shows over the position of 

 each zooid a circular area, more transparent than the intervening 

 spaces, which latter are white and more opaque, owing to the greater 

 abundance of spicules there. Thorax of zooids often dark colored. 

 Colony whitish gray. B. orbiculatum. 



Note. — The only specimens of species A and D which were found 

 incrusted branching algae, which no doubt influenced the form of the 

 colony. Colonies growing on smooth surfaces will probably be 

 found thinner and more expanded. 



