148 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



The mass of the gut is of the same form and has a similar position 

 in the two specimens. 



One would without hesitation assign both specimens to the same 

 species were it not for the different condition of the muscles. Body 

 muscles I, II, and III (our notation) are very similar in the two 

 specimens. Body muscle IV is unbranched in Apstein's specimen 

 and branched in ours. The muscle next posterior is very different 

 in the two specimens. The discrepancy would, however, be removed 

 if we were to add to Apstein's figure a posterior branch of body 

 muscle IV extending across the next posterior muscle and itself 

 giving rise to the two oblique bands which Apstein figures between 

 the gut and the atrial siphon. This would leave the fifth muscle 

 unbranched below, as in our specimen, and it should then possibly 

 be considered the basal muscle of the atrial siphon, as comparison 

 with the Cyclosalpas suggests. Comparison of Dober's (1912) and 

 Apstein's (1906, a) figures of Traustedtia radiata (figs. 138 and 139) 

 shows that the posterior branches of body muscle IV may be inter- 

 rupted in some specimens and complete in others. In similar cases 

 in other species, the potential position of an omitted or interrupted 

 muscle is indicated by the presence of a muscle blood vessel along 

 the course the muscle would take if present. 



There is such disagreement in the oral and intermediate muscles 

 as Apstein and we describe them as to necessitate treating his speci- 

 men and ours as representing distinct subspecies. The intermediate 

 muscle (Apstein's first body muscle) is described and figured as com- 

 plete across the dorsal mid line, being continuous with its fellow of 

 the other side. In our specimens it extends but a little way above 

 the angle of the mouth. Apstein says there is one sphincter muscle 

 in each lip, but he figures two in each, all four complete from the 

 angle of the mouth on one side, across the mid line, to the angle of 

 the mouth on the other side. 



In our specimens the two sphincters of the ventral lip are com- 

 plete, but the two in the dorsal lip are very rudimentary, extending 

 but a very short distance above the angle of the mouth. The dis- 

 tinctive features of Apstein's form, as compared with our specimen, 

 are, first, the smaller number and greater length of the "tentacles," 

 and the complete and conspicuous muscles crossing the dorsal surface 

 of the anterior end of the body, that is, the first and second sphinc- 

 ters of the upper lip and the intermediate muscle, very different from 

 the vestigial corresponding muscles in our specimen. These two sub- 

 species, though apparently distinct, are very similar, as much alike 

 as are the solitary forms of Salpa maxima and S. fusiformis, not so 

 closely similar as S '. fusiformis and its form aspera, which differ only 

 in the character of the test. 



