﻿SIPUNCULID WORMS OF CALIFORNIA — FISHER 385 



the spindle muscle), each on a slight pustule of the skin. They some- 

 what resemble a cluster of nematode's. 



The brain measures about 1 mm. in length and is bilobcd. It 

 varies somewhat in appearance in different specimens by reason of 

 being partly obscured by muscle fibers. 



Young. — The above description applies to the mature specimens. 

 Those under 125 mm. have a thinner body wall, translucent if at all 

 inflated. Both longitudinal and circular muscle layers are thinner, but 

 are subdivided into bundles, although the circular are sometimes 

 diflScult to see if the body wall is stretched by inflation. The circular 

 bundles then flatten and close the stomata, which lead to the in- 

 tegumental coeca, and the layer appears to ])e continuous. In well- 

 relaxed specimens the retractors are very slender, being naiTOwer than 

 the longitudinal bands of body wall. The Keferstein bodies are not 

 present in two specimens measuring 80 and 110 mm., but are present 

 in one 150 mm. long. 



T2/pe.— U.S.N. M. No. 20910, January 31 and July 18, 1931, and 

 July 19, 1933, G. E. MacGinitie collector, 8 specimens. 



Type locality. — Morro Bay, San Luis Obispo County, Calif. 



Specimens examined. — From California: 



Newport Bay, Orange County, January to February 1930, and Feb. 14, 1932 

 (with eggs), among Zostera, G. E. MacGinitie, 7 specimens. 



Elkhorn Slough, off Monterey Bay, sandy mud, low tide, G. E. MacGinitie, 

 1 specimen. 



Remarks. — 5. ingens belongs in the subgenus Siphonosomay in the 

 section lacking spinelets on the introvert. It most nearly resembles 

 S. mourense Sato (1930, p. 6, pi. 1, figs. 2-^), Mutsu Bay, Japan. 

 It differs in having circular instead of elliptical skin glands; the circular 

 muscle laj'er is divided into anastomosing fascicles; fixing muscle F 

 anchors the esophagus primarily, and not the rectum; lateral roots 

 S' S'' of spindle muscle are anchored farther in advance of the dorsal 

 retractors; nephridia open between muscle bands 4 and 5 instead 

 of 3 and 4. Sato states that there are 30 coils in the intestinal spiral; 

 if double coils are meant, the number is about the same as in ingens. 



In mourense there are 22 longitudinal muscle bundles; the ventral 

 retractors arise from muscle 3 and 4 and the dorsals from 8, 9, or 10 

 (8 in the figure). These are possible variations of .S. ingens. 



The genus Siphonomecus, in which I originally placed this species, 

 is now restricted to the type, S. mvlticinctus Fisher. It differs from 

 Siphonosoma in having only two retractors; a very conspicuous 

 nuchal organ; eight pinnate tentacular groups, of which the two ventral 

 are bifid distallj^; more complex integumental coelomic pockets; no 

 Polian villi; and a spindle muscle with three roots but of a pattern 

 entirely different from that of Siphonosoma (Fisher, 1947, p. 363, pi. 13). 



