236 BUSH 



basal spines and slender, delicately serrate blade ; setae in the other 

 fascicles slender blades. Uncini very small, with few sharp teeth. 



SPIROBRANCHUS INCRASSATUS (Kroyer) Morch. 

 pi. xxxiv, fig. 24; pi. xxxvn, figs. 25, 34. 



Spirobranchus incrassatus MORCH, Rev. crit. Serpulidarum, Natur. Tidss., I, 

 p. 405, pi. xi, figs. 21-23, 1863. EHLERS, Blake Annelids, p. 294, taf. 

 57, f. 16; taf. 58, f. 1-5, 1887. 



Type locality. West coast of United States of Colombia. 



A valve of Margaritifera sp., from the Gulf of California, in the 

 Yale Museum is covered with a mass of the tubes of this species. They 

 are of good size, variously twisted over one another, white, often with 

 markings of light yellowish brown and purplish, the high median or 

 dorsal carina often so roughened by the conspicuous growth lines as to 

 be rendered irregularly spinulose. Many of the largest tubes spread 

 along the base, forming a distinct carination on each side, along and 

 above which the surface is often punctured by the erosion of the sur- 

 face between the irregular growth lines. 



The anterior portion of the animal, with the operculum, was found 

 dried in some of the tubes. The plate on the operculum agrees per- 

 fectly with Morch's figure. Figures of the seta? and uncial plate of a 

 specimen from Acapulco, west coast of Central America, were given 

 by Ehlers (1887). 



The single example (999) from Vera Cruz, identified and figured by 

 Benedict (1886) as iS. incrassatus (Kroyer) Morch, is not this spe- 

 cies, and therefore should receive the new name Spirobranchus 

 pseudoincrassatus. The thoracic uncini are described as having from 

 1 8 to 20 teeth. 



Morch also described and figured two related forms from the 

 Pacific Ocean, near Puntarenas (Costa Rica, Gulf of Dulce), which 

 do not appear to have been subsequently noted : Hydroides {Eucar- 

 phus) crucigera Morch, on Margaritifera barbata Reeve, from 14 

 fathoms, and Pomatostegus kroyeri Morch. 



Genus Spirorbis Daudin 1800. 



Type, Spirorbis Spirorbis (Linne 1 1 760) = Spirorbis borealis 

 Daudin 1800. (See pi. xxxix, fig. 34; pi. XL, figs. 5, 6, 8, 12-15 5 

 pi. XLII, figs. 15-19.) 



Important generic characters for the animal are as follows : 

 Operculum protected by a calcareous plate, variable in form. 

 Thoracic segments usually 3, rarely 3^ or 4 (Levinsen 1883 -f Caul- 



