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Pallasia murata, n. sp. : a new British Sabellarian. 



By 

 E. J. Allen, D.Sc. 



Director of the Plymouth Laljoratory of the Marine Biological Association. 



With Plato X. 



Fragments of a large tube bitilt of pieces of coarse gravel and shell, 

 evidently the work of some Polychaite, have been constantly dredged 

 for many years on the grounds in the neighbourhood of the Mewstone 

 and Stoke Point, to the eastward of Plymouth Sound. Not until June 

 4th, 1903, was the worm first discovered to whose skill as a mason 

 these tubes are due. On that day the Laboratory fisherman captured 

 and drew attention to a tube whicli was occupied by a living worm. 

 The specimen, along with a number of fragments of empty tube, was 

 obtained on a patch of coarse gravel off Stoke l*oint. 



The species thus discovered has proved to belong to the genus 

 Paliasid, a genus which was founded by de Quatrefages to include 

 certain foreign Hermellida? (Sabellaridie) which were distinguished by 

 having two rows and not three of peristomial chtetre in the paleal 

 crown. As will be seen from the description given below, the new 

 worm most closely resembles Pallnsia Giardi, Mcintosh, from Port 

 Jackson, in Australia, and Pullada Icevispinis, Grube, from Upolu, in 

 the Pacific and from Ascension. The details of its structure, as well 

 as the large size of the British specimen, indicate that it is a new 

 species. I propose to name it l\ill(isla nivrata. My thanks are due to 

 Mrs. L. E. Sexton for the excellent drawings of the specimen reproduced 

 in Plate X. 



Tube. The pieces of tube of Fal/asia which have been dredged 

 have sometimes reached a length of four to five inches, with an 

 internal diameter of half an inch. It is doubtful, however, whether a 

 complete tube has ever been obtained. 



The tube is built of two layers, an internal layer consisting of cojn- 

 paratively small pieces of shell or thin, fiat stones, arranged with 

 considerable regularity and forming a smooth internal surface, and an 

 external layer of large pieces of gravel and shell, forming a strong, Itut 



NEW .SKRIKS. — V(il. VII. Ml. 2. U 



