582 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
is readily seen. The largest specimens range from 18 mm. to 25 
mm. in height. 
Mantle rather thin, with rather slight musculature; generally adher- 
ent to the test in alcoholic specimens. 
Tentacles of four orders quite regularly arranged except that 
those of the fourth (smallest) order are few and irregularly distributed. 
The total number in a good-sized specimen was about forty. 
Text-flg. 39. — • Dendrodoa aygregata var. pulchella (Verrill). X 2.2. 
Dorsal tubercle horseshoe-shaped; open interval forward and to 
the left, horns not incurved. 
Dorsal lamina plain and of moderate width. 
Branchial sac with four folds on each side. Of these folds, the first 
is well developed and the third also, though not so high, while the 
fourth is low, and generally flattens out before the posterior end of the 
sac is reached, and the second is generally still less developed, being 
prominent only at the anterior end, while posteriorly it is represented 
only by a small group of internal longitudinal vessels. Yet in some 
individuals all the folds reach the posterior end of the sac. The num- 
ber of internal longitudinal vessels is very variable in different speci- 
mens, as the following schemes will show. The counts were made in 
the anterior region of the sac. 
Specimen 18 mm. high. Station 2445. 
Right side 1 (15) 2 (4) 2 (8) 2 (5) 1 
mdv. en. 
Leftside 1 (12) 2 (5) 2 (7) 2 (5) 1 
Specimen 18 mm. high. Station 59. 
Right side mdv. 1 (15) 2 (5) 3 (8) 3 (5) 2 m. 
