226 



BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



brella membrane spanning between the lappets. The eight inter- 

 rhopalar grooves are 35 mm., the 8 rhopalar 16 mm., and the 16 

 intermediate clefts 31 mm. long. The eight rhopalar clefts are 

 U-shaped and the exumbrella sensory pit is at the middle of the 

 crotch of the Y with the divided groove on either side of it (see fig. 

 22, C) . The grooves between the velar lappets are simple, undivided, 

 linear clefts. 



Sixteen radial canals, eight rhopalar and eight inter-rhopalar 

 leave the central stomach, and all extend to the bell margin. There is 

 a fairly distinct ring canal about 30 mm. inward from the sense 

 clubs, and this ring canal gives rise on both its inner and outer sides 

 to an anastomosing network of vessels which connect with the 16 

 radial canals but not directly with the stomach. This network of 



FlQ. 23. LOBONEMA SMITHII FROM MANILA BAT. PART OF THE OUTER ZONE OF THE 



SUBUMBRELLA, SHOWING CANAL SYSTEM AND MUSCLE STRANDS. 



vessels extends downward throughout the length of the tapering 

 lappets trending mainly longitudinally but with frequent anas- 

 tomoses. 



The muscular system forms an annulus about 68 mm. wide in the 

 subumbrella from the margin of the arm disk to the zone of the 

 rhopalia. The circular muscles are powerfully developed and are 

 only thinned but not broken in the rhopalar radii. There are no 

 radial muscles and no muscles in the lappets (fig. 23). 



The arm-disk is 100 mm. wide, but as it was cut off I can make no 

 statements in reference to the size or form of the subgenital ostia or 

 of the gonads. 



The eight mouth-arms are separate, 150 mm. long, and each is 3- 

 winged below. The upper shaft of each arm is 60 mm. and the 

 3-winged lower part 90 mm. long. It is remarkable that each of the 

 three lateral membranes is perforated by three windows or openings 

 (see diagram A, fig. 22). The axial duct of the arm extends down 



