LIVING BRACHIOPODA. 319 



of Glottidia, though, like Glottidia, it forms a globular ball of sand about the severed end, 

 shorter and more bulbous, however. Wlieu the animal is placed on sand in a bowl with 

 water, it disappears below the sui'face in from ten to fifteen minutes. This action is 

 accomplished by oscillating the dorsal shell and raising and lowering the anterior margin 

 of the shell in a kind of shoveling motion, the lateral setae in the meantime moving 

 rhythmically back and forth, forcing the body forward and downward. If a number of 

 individuals are placed in a bowl with sand, they soon work their peduncles to the bottom 

 of the bowl where a number of loosely constructed burrows are made, which are firmly 

 adherent to the bowl (40: 11). The individuals gi'oup themselves together in a closer 

 cluster than do those of Glottidia. These tubes are often made in less than half a day, 

 and in all cases the individuals had made their tubes within the space of three days. So 

 firmly were these irregular tubes attached to the bottom of the bowl, that the sand and 

 water could be flung out by inverting the vessel, yet they all remained dangling Ijy their 

 peduncles, anchored as they were by the sand tubes in which the peduncles were encased. 

 In one experiment in which twenty-six individuals were flung upon the sand, only one 

 attached itself with the ventral valve uppermost. In other words, those that had fallen 

 upon the sand, ventral siu'face uppermost, righted themselves with this one exception. 

 After burying its peduncle, the animal comes to the surface and projects its body a third 

 of its length above the sand, sometimes lying nearly horizontal and at other times stand- 

 ing in a nearly vertical attitude. In these various positions the dorsal and ventral shells 

 are separated anteriorly, while posteriorly the beaks of the shells are brought together as 

 near as the peduncle will allow. The lateral setae now stand at right angles to the plane 

 of the body, the tips of the setae meeting (40: 15). The setae thus form an eft'ectual 

 barrier against the ingress of sand in which the inthvidual is partly buried. This barrier 

 becomes strengthened by an accumulation of mucus upon .the setae, which forms a closed 

 partition. In the meantime the three groups of setae on the anterior margin align them- 

 selves in such a way as to form three flattened oval tubes which communicate with the 

 pallial ca\aty, the central tube being slightly longest (40: 12,13). The pallium is at the 

 same time thrown into deep folds, one on each side of a median line above and below, 

 the crests of these folds coming between the base of the tubes and in some cases almost 

 meeting (45: 10). It is at precisely these points that the strong pigmentation is seen 

 which will be referred to later as probably sensitive to light. The setae forming these 

 tubes become coated with a film of mucus which apjiears to extend beyond the tips of the 

 setae and this film is continuous with the lateral jaartitions just described. The function 

 of these tubes is clearly shown when it is observed that a strong current is drawn into the 

 lateral tubes, to be as vigorously forced out of the central tube. During this attitude 

 the brachia have their lower surfaces tm-ned toward the sides of the pallial chamber, 



