74 



BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



In the upper lip there are, in the embryo figured by Streiff (fig. 50) 

 and in two of our adults, three sphincters, one, moderately broad, at 

 the edge of the lip, continuous ventral! y with the posterior edge of the 

 second sphincter of the lower lip, a second slightly broader sphincter, 

 and a third, very broad, the latter continuous ventrally with the broad 

 fifth sphincter muscle of the lower lip. The second sphincter of the 

 upper lip twists and bends back, attaching to the inside of the ventral 

 oral retractor. In two others of our adult specimens, sphincters 2 and 

 3 of the upper lip are united throughout their course, forming a very 

 broad band. The dorsal retractor is external to all the muscles it 

 crosses. The ventral retractor is external to the intermediate muscle, 

 but both its posterior extensions are internal to all the body muscles 

 they cross. 



Streiff, in describing and figuring the conditions in his embryo, 

 apparently made one slight error, failing to note the incurling of the 

 edge of the lower lip, so that the muscles of the incurled portion of the 

 lip are incorrectly given. The minute rudimentary first sphincter 

 muscle he doesn't show. His first sphincter should be number three. 

 That is, he has exactly reversed the space relations. 



The oral muscles of 

 the solitary Apsteinia 

 punctata, including 

 the dorsal horizontal 

 band between the in- 

 termediate muscle 

 and the sphincters of 

 the upper lip, are 

 rather similar to those 

 described for the Cy- 

 closalpas and Ritte- 

 rias, showing no im- 

 portant differences 

 except the great pos- 

 terior extension of the 

 dorsal and ventral 

 branches of the ven- 

 tral oral retractor. 

 This is a remarkable 

 feature. Streiff, how- 

 ever, shows for the 



Fig. 62.— Apsteinia. punctata, solitary form, atrial mdsculatuke, solitary form of Cy- 



SEEN FROM THE LEFT SIDE. FROM STREIFF (1908). dosdlpa virguU & Veil- 



tral oral retractor which is split posteriorly into dorsal and ventral 

 branches. These branches extend back only to the first body mus- 

 cle. In our specimens of the solitary Cyclosalpa virauln the ventral 

 oral retractor is undivided (pi. 11, fig. 26). 



a.r. 



