THE SESSILE BAKNACLES. 299 



segments. In a specimen from station 2004 the terminal tuft of 

 spines on each ramus contains one broad, serrate spine with a pair of 

 large teeth (fig. 8'2&). The specimen dissected from Ocean City has 

 rami of 9 and 6 segments, the terminal tufts having several serrate 

 spines (fig. 82e), and there are others of less characteristic shape 

 on several of the later segments. 



The cirri iii to vi have segments with four pairs of spines (fig. 



This species differs from C. stellatus by its smoother wall, usually 

 covered with an epidermis, by the shape of the articular rib of the 

 scutum, and the much broader lower part of the tergum. In the 

 specimen of stellatus I dissected there are no such strongly modified 

 spines on the second cirri, and the later cirri have five pairs of 

 spines, fragilis having four. 



The specimens growing on rushes (pi. 70, figs. 1-Id, 4). are usually 

 elongated, and sit with the carinorostral axis lengthwise of the rush. 

 In hundreds examined, the parietes are never ribbed. 



In a group on an oyster (Ostrea parasitica Gmelin) from Varadero 

 Park, near Cardenas, Cuba, collected by Dr. J. W. Ross, the con- 

 tour is usually shorter and the surface is either smooth or furnished 

 with round radial ribs. There are also transitional forms. The 

 scutum has a longer basal and shorter tergal margin than in the 

 Florida examples on rushes, and the opercular valves are beautifully 

 rose colored inside. Exterior dull olive or olive brown, not corroded, 

 length G, width 5 mm. (pi. 70, figs. 3-3<?). I did not examine the 

 mouth parts and cirri. 



Another group, on a pebble from Charlotte Amalie, St. Thomas, 

 collected by Mr. Silas L. Schumo, consists of smaller but similar 

 specimens. 



A large series from Jamaica (C. B. Adams) is on the shell of an 

 Atrina, and on broken coconut shells. They agree with the 

 Cuban lot in form and color and are mainly smooth, but with some 

 individuals having low, rounded ribs. The opercular valves are 

 white within, but otherwise like the Varadero Park lot. Some Ba- 

 lanus ampliltr'de grow among them. 



In the large series from Esperanza, Cuba, the adults have many 

 strong, unequal ribs, and measure up to 13 mm. in diameter, 4.3 mm. 

 high. The walls are thick, and the basal margins are deeply folded. 

 Individuals of half that size resemble the rougher examples in plate 

 70, figure 3<?. The opercular valves are considerably eroded. 



At Ocean City, N. J., this species was found by Mr. Fowler grow- 

 ing on Balanus balanoides, the largest specimens 5 mm. in greatest 

 diameter (pi. 70, fig. 2). The contour is more rounded than in those 

 growing on reeds- and the surface is not so smooth. The basiscutal 

 angle of the tergum is some\vhat cut out, the articular ridge short 



