PAUMOTELLA. 481 



Spirobranchus Blainville. 



Bull. Soc. phi!., 1818, p. 79; Oken's, Isis, 1818, p. 2062. 

 Cymospira Blainville, Diet. sci. nat., 1828, 57, p. 431. 



Spirobranchus tricornis (Morch). 



Spirobranchus giganteus Pallas, var. tricornis Miirch, Naturh. tidsskr., 1863, ser. 3, 1, p. 404. 

 Spirobranchus tricornis Ehlers, Mem. M. C. Z., 1887, 15, p. 292, pi. 57, fig. 8-15. 



A single large specimen, which unfortunately had at some time been dry, 

 is in the collection. It has an extreme length, inclusive of the branchiae, of 

 about 113 mm., the abdomen measuring 83 mm. The abdomen narrows 

 unevenly from the anterior end caudad; in its present shrunken condition the 

 width at the anterior end is 7.5 mm., and that near the caudal end 3.2 mm. 

 The color in general is similar to that frequent in S. giganteus and other close 

 relatives of the West Indian region in having the anterior portion of the collar 

 and much of the branchiae of a dark violet-brown color; the abdomen is some- 

 what greenish yellow. The calcareous plate of the operculum is almost circular, 

 being slightly longer than wide {cir. 12 mm. X 11 mm.); the horns have the 

 usual general structure and proportions. The collar ventrally is entire and 

 produced cephalad, not incised as in giganteus. The uncini conform to type. 



The tube is large, thick-walled, and but little curved. It is three-sided 

 in cross-section, subtriangular. The smooth-walled bore has at one end, where 

 broken off, a diameter of 10 mm. and at the other, where also broken off, a diame- 

 ter of about 8 mm. 



Locality. Panama. 12 March, 1891. 



Paumotella, gen. nov. 



Operculum obconic, the distal surface slightly depressed within the margin 

 but not infundibuliform, mesally weakly convex, without processes; margin 

 entire, smooth. 



Thorax consisting of seven setigerous somites. 



Collar entire ventrally; sharply incised on each side. 



Thoracic membrane well developed. 



Thoracic setae ahke on all somites, no special ones on the collar. Setae 

 of thorax coarse, limbate, acutely tapering forms and fewer fine capillaiy ones. 

 Uncini with teeth numerous and fine, the series ending on the side nearest 



