9G2 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [36] 



Mesonema Bairdii, sp. UOV. 



Specimens examined. 



Disk flat, discoidal, with smooth exunibral surface. jS'o indication in 

 alcohohc specimens of a coronal furrow. Diameter of disk 80-100'^"^. 

 In one specimen there are twenty-nine tentacles. The tentacles lie on 

 the bell margin, regularly ]>laced at tlie peripheral terminus of a chy- 

 miferous tube. As a rule, between the tubes which end at the bases of 

 a tentacle in this way there are three chym iferous tubes. Tentacular 

 bulb slightly inflated, or globular. Tentacles short, dark-brown color. 

 Between the tentacular bases on the bell margin, rounded bodies, prob- 

 ably marginal sense-bodies, are seen. Excretionary o]ienings not via- 

 ble. The velum is thin, narrow. The bell margin pigmented of the 

 same color as the tentacles and tentacular bases. Seen from Siibumbral 

 side, M. Bairdii has in one specimen one hundred and sixteen ovaries, 

 extending the whole distance along the same number of chymiferous 

 tubes. Ovaries slightly convoluted from the peripheral subumbral 

 margin to the walls of the stomach about a half of the whole radius 

 of the medusa. They are separated from each other by a smooth por- 

 tion of the subambrella, which is destitute of the i)apill8e described in 

 PoJycanua {Zi/f/odacfi/Ia) Granlandicd. In the walls of this region of 

 the snbnmbrella occur small white (muscular) threads. 



The walls of the stomach hang down from the subumbral side of the 

 disk, and aie fimbriated at their free end or margin by the character- 

 istic labial tentacles, which are closely crowded together. The number 

 of labial tentacles equal that of the chymiferous tubes. Extensions 

 from the openings of these tubes into the stomach are continued in the 

 form of mesenteric structures, which end in the labial tentacles. These 

 mesenteries are probably folds in the stomach walls. Intermediate be- 

 tween these extensions on the stomach walls are strongly developed 

 nuiscular fibers joining each i^air. 



The labial tentacles are so short that they can be with the great- 

 est difiiculty brought together to close the aperture of the mouth. The 

 apertures of the chyiniferous tubes into the stomach have the form of 

 slit-like openings, which lie between the mesenteric folds on the inner 

 side of the stomach walls. When seen frou) the subumbral side the 

 slit like channels reseu?ble continuations of the radial tubes. 



I dedicate this species, M. Bairdii^ out of great respect, to Prof. S. 

 F. Baird, of Washington, 



