vol. 2. ft. 2.] A TAXONOMJC STUDY OF THE SALPIDAE- — METCALF. 131 



lip. The ventral branch of the dorsal oral retractor is continuous 

 only with the second sphincter of the lower lip. 



The dorsal branch of the dorsal oral retractor is continued forward 

 into the first sphincter of the lower lip and also gives rise to a short 

 muscle on each side, which runs up onto the upper lip, as if to form 

 a first admarginal sphincter, but this is incomplete. 



The musculature of the atrial siphon is shown in part in figure 121, 

 which is a drawing of the siphon of an embryo cut open on the mid- 



A 



a.o. 



B 



Fig. 119.— Pegea confederata, solitary form: A, dorsal view; B, view from the right side. 

 X 2 diameters. From specimens collected in Phillppine waters and others from the Alaska 

 coast. (Drawn by IIoyt S. Hopkins.) 



dorsal line and spread out flat, the drawing showing an exterior 

 (ventral) view of the preparation. Figure 122 shows a similar 

 preparation of the cloacal siphon of an adult, in similar view. 



Figure 119, A and B, show additional muscles on the dorsal side 

 at the base of the atrial siphon. These do not appear in figures 121 

 and 122. There is a slightly developed atrial retractor muscle, con- 

 tinuous, in the embryo, with the second dorsal sphincter, in the 



