420 HOMES WITHOUT HANDS. 



ful lid," in allusion to the elegant structure of the operculum and 

 its complement of horns. 



In another genus, which has been called Placostegus, the oper- 

 culum is calcareous, flat, and rounded, looking so like the opercu- 

 lum of some aquatic mollusc that it might easily be mistaken for 

 that object. The genus is so named on account of the shape of 

 the operculum, and the word is of Greek derivation, signifying 

 Plate-roofed. 



One species of this genus, Placostegus carinatus, is remarkable 

 for a peculiarity which has been brought forward by Dr. Baird, 

 in a paper read before the LinnEean Society in April, 1864. " I 

 wish particularly to bring before the notice of the Society the 

 fact that the animal gives out a beautiful dye or color. The 

 specimens which were the subjects of my examination had been 

 for a number of years in the British Museum, some having been 

 placed there in 1845, and others in 1847. Notwithstanding their 

 having been so long dry, when softened in water, taken out of 

 the tubes and placed in spirits of wine, they imparted to the 

 liquid a beautiful and delicate red tint." 



The specific title of carinatus, or keeled, is given to the animal 

 because its tube has a decided keel or ridge upon its upper sur- 

 face. The color of the animal is blue, and the fan-like tuft of 

 gills is blue banded with white. An allied species, Placostegus 

 latiligulatus, is remarkable for the shape of its tube, which is de- 

 fended at the orifice by a kind of pent-house or hood, which pro- 

 jects boldly from the upper edge, just like the peak of a boy's 

 cap. 



Another genus of Serpulse, called Cymospira, has the opercu- 

 lum horny, elliptical, and furnished with two or more large 

 toothed horns, which are generally placed near the hinder edge. 

 Some of the species are very large — one, which is in the British 

 Museum, being as thick as a man's finger, and being inhabited 

 by a Serpula three inches in length, and more than a quarter of 

 an inch in diameter. Sometimes the horns are long and boldly 

 projecting, and sometimes the tube has a pointed projection like 

 the hood which has already been mentioned. One of the short- 

 horned species which was procured from Swain's Eeefs, on the 

 eastern coast of Australia, was always so imbedded in corals and 

 madrepores that the true shape of its tube can not be ascertained. 



Perhaps the most extraordinary example of the operculum is 

 furnished by the genus Pomatostegus, in which the operculum is 



