134 



COE 



the proboscis sheath Itself does not extend backward behind the ante- 

 rior third of the intestinal region. 



Body musculature consists of the usual circular and longitudinal 

 layers, and presents few peculiarities save that the inner circular layer, 

 which is found in the esophageal region, is remarkably thin, and 

 does not exhibit distinct dorsal or ventral crossings with the outer cir- 

 cular layer, as is the case in several other species of the genus. 

 Immediately in front of the nephridial openings the inner circular 

 layer becomes several times as thick as it is anteriorly, while it disap- 

 pears almost entirely just at the beginning of the intestinal region. The 

 circular muscles of the proboscis sheath present a similar increase in 

 strength in the same region, and are directly continuous with the inner 

 circular muscles of the body wall (text-fig. 17, icni). These thick- 

 enings correspond in nature and position with the enormously tliick- 

 ened internal circular muscles in Carinoma. 



Blood System. — Lacunae in head and lateral vessels present no 

 peculiarities. The jDair of vessels situated witliin the proboscis sheath 

 originate anteriorly just behind the mouth and extend back nearly 

 half way to the intestinal region, being connected with the lateral ves- 

 sels at frequent intervals. Their walls are thickened, much con- 

 voluted, and appear to be somewhat glandular in nature. 



Nephridia. — The nephridial tubules are limited to about the third 

 quarter of the esophageal region. They do not extend forward quite 

 as far as the posterior ends of the proboscis sheath vessels. Their 

 anterior branches are numerous, but of small size. They project in- 

 ward from the lateral walls of the lateral blood vessels, very mvich as 

 in Carinoma. The main longitudinal canals are large, and are situ- 

 uated in the parenchyma above the lateral vessels, and slightly separated 

 from them. There is a single main longitudinal canal on each side, 

 and this is usually about half the diameter of the lateral vessel in the 

 same region. At its posterior end each of the longitudinal canals en- 

 larges somewhat, and as usual sends off a large efferent duct {nd^ text- 

 fig. 17) to the dorso-lateral aspect of the body. 



Nervous System and Sense Organs. — The cerebral sense organs 

 are well developed for the genus, although they are not distinctly sepa- 

 rated from the other nervous tissues, as in the case of C. rzibra} 

 Yet there is a distinct ciliated canal leading from a specialized lateral 

 furrow into the nervous tissues above and beside the dorsal brain lobe. 

 The inner end of this ciliated canal (p1. xxii, fig. 2, cc) passes within 



'Coe, Proc. Wash. Acad. Sci., in, p. 13, pi. x, fig. 2, 1901 ; also previous 

 article, paged identically. 



