vol. 2, pt. 2.] A TAXONOMIC STUDY OF THE SALPIDAE METCALF. 69 



are much broader than the rest of the fibers of the band. The more 

 distal sphincters have their fibers, 2 to 10 in number, uniformly nar- 

 row. All the inner fibers in all the muscles are narrow. 





a.i: 



Fig. 43.— Bitteria hexagona, aggregated form: A, atrial muscles viewed from the right side; 



B, DETAIL SHOWING ATTACHMENT OF THE SPHINCTERS TO THS ATRIAL RETRACTOR MUSCLE. (DRAWN BY 



Hoyt S. Hopkins.) 



\en. 



Fig. 44.— Bitteria hexagona, aggregated form, gut seen from the right side, x 3 diameters. 



(Drawn by Hoyt S. Hopkins.) 



The gut (fig. 44) forms a somewhat compact "nucleus," as in the 

 aggregated zooids of Ritteria amboinensis, but the course of the intes- 

 tine can be seen without ^dissection. Its condition is closely similar 

 to that in the solitary form except that the intestine is shorter. 



