102 HYATT, 



site wall (PI. 11, fig. 1, B). These were few in number, 

 and were seen only in one specimen on the abdominal side. 



There is a highly interesting series of muscles described 

 by Dumortier and Van Beneden in the ccenoecium of Fred- 

 ericella, called by them " Short Retractors," which resemble 

 these. They are attached to the alimentary canal, and 

 bear about the same relation to the stomach that the abnoi- 

 mal fibres of Pectinatella do to the oesophagus (PI. 11, 

 fig. 1 , R.) . These reticulating fibres dispersed thrbughout 

 the interior bear a certain likeness to the network of mus- 

 cles in the ccenoecium of Cristatella. They difier materi- 

 ally, however, in having the posterior extremities attached 

 to the alimentary canal instead of to the upper walls of the 

 ccenoecium. 



In the lophophore there is a pair of large muscles, 

 one in each arm, which I have called the Lophophoric 

 Flexors (PI. 13, fig. 13, M). They arise from the oral 

 region, and proceed on either side to the extremities of the 

 arms, buried in the substance of the lophophore, and bor- 

 dered on their outer sides by the nerves. They elevate 

 the tips of the arms, or bend them in an anterior direc- 

 tion . 



The agency of a pair opposing the lophophoric flex- 

 ors is recognizable every time the tips of the arms are bent 

 anteriorly, but no bands of fibres were observed in the floor 

 of the arms, which could have caused these movements. 

 The lophophoric flexors liave been described and figured by 

 Dumortier and Van Beneden as a fascicle of the retractors. * 

 This, -however, I believe to be erroneous, since, in Pectin- 

 atella and Cristatella, the oesophagal retractors, although 

 attached to the inside of the arms for some distance in 

 advance of the mouth, do not mingle their fibres with, or 

 approach those of the flexors in the centre of the arms, 

 but terminate on the sides just below the bases of the 

 tentacles. 



By all other authors, who have seen them, they have 

 been confounded with the lophophoric nerve-branches. 



* Op. cit. p. 86. pi. 4. 



