16 DR. W. BATED O^ NEW TUBICOLOUS AKNELIDES. 



4. Placostegus Gkati, Baird. (PI. I. figs. 4, 4«, h.) 



Char. Animal, operculo excepto, ignotum. Operculum corneum?, eir- 

 culare, concavum. Tubuli flexuose repentes, depressi, valde rugosi, 

 dorso late carinati, carina haud in ligulam os supra extensam desinens. 



Hub. ? (Mus. Brit.) 



The ouly specimens we possess in the collection of the British 

 Museum are a few tubes creeping on a stone. The operculum 

 was found in two or three of the tubes, and, unlike the others 

 belonging to the genus Placostegus, appears to be horny, of a cir- 

 cular form, aud hollow or concave on its upper surface. The 

 tubes are flexuose, very rugose, and possess, like the last-de- 

 scribed species (P. latiligulatus) , a rather broad flat keel along 

 the back of the shell. This keel is very rugose or wrinkled, and 

 does not extend beyond the mouth of the tube, which is quite 

 circular (fig. 4 h). The form of the tube is very irregular, and in 

 several specimens at the larger extremity it is cemented as it were 

 by a smooth, hard calcareous secretion to the stone to which it is 

 attached. The specimens were presented many years ago to the 

 Museum by Dr. Gray, whose name I have attached to the species. 



EXPLANATION OF PLATE I. 



Fig. 1. Heteronereis signata, natm-al size ; 1 a, one of anterior feet ; 1 h, one 

 of posterior feet ; le, seta of ditto ; 1 d, head and 8 first segments of 

 body : all magnified. 



Fie. 2. Uwpomahis Boltoni, natm-al size, on Haliotis ; 2 a, operculum of ditto ; 



2 h, one of the spikes of ditto : both magnified. 



Fig. 3. Flacostegus latiligulatus, nat. size ; 3 a, operculum of ditto : magnified ; 



3 &, extremity of tube, nat. size. 



Fig. 4. Flacostegus Gragi, nat. size ; 4 a, operculum of ditto : magnified ; 4 b, 

 extremity of tube, nat. size. 



Part II. 

 (Plate II.) 

 [Read June 2, 1864.] 

 Genus Ctmospika, Savigny. 

 Amongst the tubicolous Annelides belonging to the family 

 Serpulidse, the genus Cymospira of Savigny is remarkable. The 

 branchiae are described by Pallas and others as being very beau- 

 tiful when seen in the living animal, and are rolled into spires of 

 several turns. The operculum consists of a somewhat horny, 

 elliptical, shallow plate, which supports two or more dentated 

 horns or processes, generally near its hinder margin. The tubes 

 of all the known species, of which only three or four have been 

 described, burrow into or are attached to masses of Madrepore 



