DR. W. BAIBD ON LEPIDONOTTJS CIBEATUS. 161 



Description of a New Yariety of Lepidonotus cirratus parasitic in 

 the Tube of Chcetopterus insignis. By W. Baibd, M.D., P.L.S. 



[Eead December 15, 1864.] 



In" the last volume of the ' Linnean Transactions ' I described a 

 new species of Ghcetopterus as British, and, at p. 485, Mr. Williams 

 of Beaumaris, in his notes upon this Annelide, mentioned that 

 generally speaking a species of Lepidonotus {Polynoe) was found 

 by him living parasitic in the tubes of that animal. In a short 

 note I mentioned that the parasitic worm was a variety of L. 

 cirratus. I now beg to lay before the Society a fuUer description 

 of it. 



Lepidonottjs cirratus. Var, parasiticus, Baird. 

 Body about 1| inch long, and at the widest part, including the 

 setae of the feet, 6 lines in breadth. It is slightly narrower near 

 the anterior extremity. The scales are fifteen pairs. They cover 

 the whole body, increase in size as they descend from the head, 

 near which they are small, nearly circular in form ; afterwards they 

 become reniform and are covered with innumerable very small 

 rough points, which are scarcely visible without the assistance of 

 a glass of low power. The external edge is ciliated, or fringed 

 with short clavate hairs. The head is concealed by the upper 

 pair of scales. Eyes four in number ; the upper pair wider apart 

 than the lower. Of the three antennae, the central or odd one is 

 setaceous, suddenly terminating in a long, slender, sharp point, 

 and beset with rather numerous short clavate hairs. The lateral 

 pair are shorter than the central one, setaceous, smooth, the lower 

 half conical in form, stout, marked across with a double purple 

 streak, and, like the other, terminating suddenly in a long slender 

 white point. Palpi very stout, especially near the base, setaceous, 

 terminating more gradually in a point, and quite smooth. Tenta- 

 cular cirri setaceous, and like the central antenna terminating 

 suddenly in a long slender point, and beset with short clavate 

 hairs, but with no enlargement or swelling near the apex. These 

 organs are all short, and nearly of equal length, though the palpi 

 are somewhat the longest and much the strongest. The cirri of 

 the second pair of feet are smooth and setaceous ; all the others 

 are longer, setaceous, ringed with black below the apex, but with- 

 out any swelling or enlargement there, terminating in a slender 

 sharp point and beset with short clavate hairs. The caudal cirri 

 are short. The feet are thirty-seven pairs in number. The dorsal 



