POTAMILLA TOEELLI. 241 



The distribution is wide :— Cape Agulhas and Antarctic Seas (Ehlers) ; Iceland 

 (Malmgren) ; Canary and Madeira, young as P. incerta (Langerhans) ; Southern Japan 

 (Marenzeller) ; amidst Cynthia glomerata and the tubes of Pomatoceros triqueter , -and 

 smaller forms also dredged on oyster shells at Dinard (De St. Joseph); Canada 

 (dredged by Whiteaves) ; shores of France and Monaco (Fauvel) ; Hawaiian Islands 

 (Tread well). 



The general aspect of the cephalic plate when the branchiae are removed agrees with 

 that of its allies, and in the preserved examples some have a prominent T-shaped 

 projection formed by the developing bases of the branchiae— a condition not observed in 

 other forms. The collar has a narrow slit dorsally, then it extends on each side laterally 

 and ventrally with an even edge to the ventral somewhat triangular lamellae, which are 

 reflected in protrusion, and which are separated from each other by a deep V-shaped 

 notch. JNTo eyes are visible in the spirit-preparations from Britain or from Canada. In 

 the young forms the pinna3 develop as papillae and the terminal filament appears to be 

 slightly webbed — that is, has a thin border at each side. Moreover in some young examples 

 the terminal process is moniliform — it may be from diminished vitality. 



The branchial filaments are of moderate length and are opaque white in life, pale in 

 the preparations. The structure of each filament is typical, and it ends in a short, thick 

 process distally. The pinna? are of average length, and it is only at the tip of the organ 

 that shorter forms occur, the last ten or twelve gradually diminishing to end in a short 

 papilla-like rudiment at the base of the distal process. The number of the filaments 

 appears to be from twelve to fourteen in each fan. 1 



When the oral region is in a state of expansion a fold passes on each side from the 

 ventral lamellae upward and its end fuses with the middle of each branchial fan, and 

 indeed appears to be the only representative of the tentacle of other forms. Malmgren 

 states that it is very short, broad and sub-circular. This fold is quite separate from the 

 ventral edge of the basal tissue of the branchiae. On the other hand, a considerable 

 portion of each dorsal edge of the base of the branchiae is bordered by a free and mobile 

 flap — the ventral edge adjoining the mouth. 



The body (Plate CXIV, fig. 3) is of small size in the examples from Plymouth, viz. 

 about an inch in length and of the thickness of stout thread, whereas in the Canadian 

 forms it is between 2 and 3 inches long and as thick as a crow-quill. De St. Joseph 

 also found large examples at Rocher-Vide. It is grooved dorsally in the anterior region, 

 rounded posteriorly, whereas the ventral surface is more or less flattened and marked by 

 the median groove from the anterior region backward. The first region has a variable 

 number of segments, viz. from five to eight (Langerhans — seven to nine). The posterior 

 region has from thirty to fifty. Toward the tail it is flattened and tapered to end in the 

 anus, which often presents a lateral projection. De St. Joseph describes the body as 

 brownish with large spots of white. The first segment has two oval eye-spots (Langerhans). 

 Fauvel 2 describes anal eyes, which are absent in the preserved examples from Plymouth. 3 

 The first bristle-bundle consists of simple bristles with moderately tapered tips and distinct 



1 Langerhans (1884) notes that the branchias (as in other Sabellids) are regenerated. 



3 'Campag So./ p. 315. 



3 Both are seen in small specimens kindly sent by Major Elvves from Bahbacombe. 



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