vol. 2. pt. 2.] A TAX0N0MIC STUDY OF THE SALPIDAE METCALF. 153 



The posterior branch of body muscle IV is crossed by a band 

 which may be a fifth body muscle, or perhaps a basal atrial sphincter 

 lying across the dorsal side of the base of the atrial siphon. Just 

 beyond this band, body muscle IV, & divides into two branches as in 

 the form cristata, one branch passing behind the visceral mass, the 

 other running below the atrial siphon, where it meets its fellow from 

 the opposite side, thus forming a basal atrial sphincter on the lower 

 side of the siphon. The other atrial muscles are not well shown by 

 Apstein, and I am not quite sure of them in Dober's figure. 



Fig. 139.— Tbanstidtia radiata, solitary form, dorsal view, x 3$ diameters. From Apstein 



(1906, 6). 



The intermediate and oral muscles are quite differently figured by 

 Apstein and Dober. The former shows what seems to be a very 

 short intermediate muscle, a short oral retractor, and one complete 

 sphincter in each lip. Dober's figure is not clear. It shows more 

 muscles than Apstein depicts. Among them are a short intermediate 

 muscle, an oral retractor, a delicate admarginal sphincter, which 

 is complete, and a broader incomplete second sphincter, both in the 

 lower lip, a broad complete first sphincter and an aborted very short 

 second sphincter in the upper lip. This musculature is considerably 



