LIVING BRACHIOPODA. 353 



channels. Shipley ('83) finds the same condition in Cistella ; he says, " The blood 

 is contained in a number of vessels which run irregularly in the tissues of the body, but 

 which chiefly lie in the mantle and that part of the body wall lining the shell. It is not 

 possible to make out very distinct walls to these vessels which appear to be mere slits in 

 the tissue." The pallium of L. lepidula shows marked differences from that of Glottidia 

 in the disposition of the main pallial sinuses and of the smaller lacunae (53 : 8) . In L. 

 letpidula, the main sinuses run nearer the lateral margins of the pallium, and their termi- 

 nations are wider apart than in Glottidia ; furthermore the sinus has a uniform outward 

 curve. The lacunae, which run off to the right and left with such regularity in Glottidia, 

 are irregular and branched. The difference is of that kind mentioned by Hancock in a 

 species winch he distinguishes as L. affinis in contrast to the pallium of L. anatina. In 

 L. lepidufa, the lacunae, as they branch from the great sinus, appear tubular (53: 11, 12). 

 In figure 12 an outline of the animal, natural size, is given, with dotted line to indicate 

 the point from which the greatly magnified drawings of the lacunae are made. The ridge 

 of ciliated epithelium appears like an acute pyramid with apex inclined backward. On 

 each side of the circular outline of the lacuue, appear smaller sections of other structures, 

 whether of lacunae or not, I was unable to ascertain. The courses of the currents in 

 53 : 8, which are indicated by arrows, are precisely the same as seen in Glottidia. My notes 

 record no appearance of the gill ampullae. At the proximal end of the great pallial sinus 

 is seen the opening which apparently leads to the perivisceral cavity. It is a long, 

 narrow opening, lying oblique to the median line (53: 8,9,10). Near the inner side of 

 this slit-like opening is seen the otocyst ; small lacunae appear in the immediate vicinity 

 but their outlines are not clearly made out. The blood pours out of this opening in a 

 vigorous current on the inner side, runs along the inner side of the great pallial sinus, 

 coursing through all the lacunae successively and then returns on the outer side, following 

 up and down each lacune in turn. As the current approaches the main pallial opening, a 

 part of the current is diverted to the outside of the lateral sinus, where it runs to the 

 posterior end of the body to return on the inner side of the sinus, back to the main pallial 

 opening into which it is directed. The sinuses, lacunae, and all details are symmetrically 

 developed on each side of the median line. In 53: 9,10, is represented the right 

 opening into the sinus with a portion of the right sinus as seen from the dorsal surface. 

 The anterior wall of this opening seems to be continuous with the perivisceral wall. This 

 opening abruptly closes at intervals, entirely checking the flow of the blood, and the 

 corpuscles immediately dam up the entrance both inside and outside, showing that the 

 action of the ciliary ridges is not arrested. As the openings slowly part, an impetuous 

 rush of the corpuscles takes place, and while these remain open, the blood circulates with 

 great rapidity (53 : 10) . This closing of the openings takes place the moment the shells 



