16 DR. W. BAIHD ON NEW TUBICOJ,OUS ANJ^ELIDES. 



4. Plaoostegits Grayi, Baird. (PL I. iigs. 4, 4«, h.) 



Char. Animal, operculo excepto, igiiotum. Operculum corneura ?, cii- 

 culare, concavum. Tubuli flexuose repentes, de]3ressi, valde rugosi, 

 dorso late cavinati, carina iuiud in ligulam os su})va exteusam desinens. 



Hub. ? (Mus. Brit.) 



The only specimeus we posisess in the collei-tiou of the British 

 Musenm 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, and hollow or concave on its upper surface. The 

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

 Bcribed species (P. latiUgulatus) , 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. Grra}^ Avhose name I have attached to the species. 



EXPLANATION OP PLATE I. 

 Fig. 1. Heleronereis signata, initm'al size ; 1 a, one of a:iterior feet ; 1 b, one 



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



body : all magnified. 

 Fig. 2. Eiipomatus Boltonl, natural size, on Haliotis ; 2 a, operculum of ditto ; 



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



Fig. 3. Placostegiis latiligulatus, nat. size; 3 a, operculiun of ditto : magnified; 



3 b, cxti'emity of tube, nat. size. 



Fig. 4. Placostegus Qr ay i, n&t. size ; 4 «, operculum of ditto : magnified; 4 6. 

 extremity of tube, nat. size. 



Part II. 



(Plate II.) 



[Read June 2, 1864.] 



Genus Cymospira, Savigni/. 



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, whicli supports two or moi-e dentated 

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

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

 described, burrow into or ai'c atlached to masses of Madrepore 



