322 



BULLETIN 93, UNITED STATES NATIONAL MUSEUM. 



pressor muscle pit is generally but not always crossed by short 

 crests, as in several other West Coast species. 



The tcrgum is concave within. The spur projects in a blunt point 

 below the basiscutal angle. There is a narrow, basicarinal lobe, 

 with a few short crests for the lateral depressor muscle. 



The labrnm is concave in the middle, and has many long hairs 

 at the sides. 



The mandibles and maxillae (fig. 96&) do not differ materially from 

 those of C. stcllatus. 



Cirrus i has rami of 7 segments, the anterior ramus longer by two. 

 The posterior edge of the lower segment of the anterior ramus 



Fu;. OS. CHTHAMALUS cinitATus, SAN LOKUEXZO ISLAND, a, BASAL SEGMENTS OF THE RAMI 



OF CIRRUS II, THE ANTERIOR MARGIN TOWARD THE LEFT. b, EDGE OF THE MAXILLA. 

 C, ELEVENTH SEGMENT OF CIRRUS VI ; ONLY THE OUTER SPINE OF EACH PAIR IS DRAWN. 



bears a series of about six obliquely conic teeth, reminding one of 

 those of Acasta. 



Cirrus ii has rami of 8 and 6 segments. The anterior ramus is 

 longer by about two segments, and on its lower segment bears a 

 series of conic teeth directed toward the posterior ramus (fig. 96a). 

 Several succeeding segments have one or two similar teeth. 



Cirrus iii has very unequal rami of 16 and 30 segments. Those of 

 the distal third of the longer ramus are very slender and bear only 

 a few slender spines near their distal ends. The other segments are 

 armed with six pairs of spines. Darwin states that he found the 

 rami equal in one specimen. The later cirri have subequal rami, the 

 segments bearing six pairs of spines (fig. DGt). 



There is not much variation in the opercular valves, but much 

 more in the wall. In one specimen from San Lorenzo Island the 

 wall is rather thin, not ribbed, and covered -with a dark olive-brown 

 cuticle in the lower part. The upper part is corroded. The interior 

 is smooth, and the sutures are distinct. The long slope of the articu- 



