368 PROCEEDINGS OF THE NATIONAL MUSEUM Yor. 9? 
teries are inconspicuous, and their posterior border has a muscular 
strand continued upon the sides of the esophagus. The contractile 
vessel is posteriorly densely papillated, and its posterior end is con- 
siderably behind the point where the esophagus becomes attached to 
the rectum. Just back of this point the esophagus has a special 
muscular frenulum (fF), which is anchored by a fork spanning the 
nerve cord well in front of the attachment of ventral retractors. 
In S. multicinctus this frenulum anchors the rectum. The intestinal 
spiral is very long and sometimes reaches nearly to end of body. 
There are 60 to 62 spirals of the canal counted consecutively. 
Plate 14, figure 3, and plate 15, figure 3, show the relations of esoph- 
agus, rectum, and spindle muscle in the type and paratype. The 
spindle muscle arises in front of the anus, and after passing backward 
through the intestinal spiral (which in the type extends to within 
65 mm. of the end of body) it sends off numerous branches, which 
are attached to the longitudinal bands ventrally, laterally, and dor- 
sally, while a small strand continues to the, posterior extremity. 
Where the esophagus joins the rectum there are two symmetrical 
lateral branches (/’) attached in front of the dorsal retractors to 
the first muscle bundle external to that from which the dorsal re- 
tractors arise. There is no coecum. The wing muscles are fairly 
conspicuous—rather better developed than in S. multicinctus. 
At the extreme posterior end of body are four (or five) slender, 
terete, fusiform bodies, which open close together (around the end of © 
spindle muscle) each on a slight pustule of the skin. They somewhat 
resemble a cluster of nematodes. 
The brain measures about 1 mm. in length and is bilobed. It 
varies somewhat in appearance in different specimens by reason. of 
being partly obscured by muscle fibers. 
Type.—U.S.N.M. No. 20910. 
Type locality—Morro Bay, San Luis Obispo County, Calif., 8 
specimens. G. E. MacGinitie collector, January 31 and July 18, 
1931, and July 19, 1933. 
Specimens examined.—Newport Bay, Orange County, Calif., 7 speci- 
mens, among Zostera, G. EK. MacGinitie, January—lFebruary 1930 
and February 14, 1932 (with eggs).. Elkhorn Slough, off Monterey 
Bay, Calif., 1 specimen, sandy mud, low tide, G. E. MacGinitie, 
Remarks.—This species and S. multicinctus are so different in most 
of the details of internal anatomy that one may question their close 
relationship. The muscles of the body wall and the subdermal canal 
system, fed by transverse lacunae in the circular layer, are essen- 
tially the same in the two species. It is curious that the muscular 
anchor F (pl. 13, fig. 1; pl. 14, fig. 3) is so similar in the two species. 
