446 THE OPISTHOBEANCHIATE 



fused, being united by theii' bases and at their tips, leaving an en- 

 closed space in tlie middle. The tips of these double teeth are 

 broad, flat, and triangular. On the other side of the radula there 

 is a row of double teeth resembling those just described, and also a 

 row of large teeth formed in exactly the same way by the fusion of 

 three of the ordinary slender hook -like teeth. 



Another specimen was dredged near the Duke Eock on September 

 24th, 1890, measuring H inches long by -f|- broad when at rest, and 

 1^ inches by-j^ inch when en marche. Colour precisely as in Alder and 

 Hancock's figure. Gill-plumes, exactly as in the previous specimen, 

 protruded from the wide fossa in two separate tufts, one on each 

 side. Each of these lateral tufts was formed of three plumes, the 

 third on each side being distinctly trifid and very broad, and all 

 the plumes very pinnate in character. On several occasions I saw 

 the tuft of one side retracted independently of the other, pointing 

 to a power of independent contraction of the branchial retractors of 

 each side. This division of the branchial plumes into two independ- 

 ently retractile halves is a very marked character, and has not, I 

 believe, been recorded before. 



This genus is distinguished from the Aldisa^ of Bergh, among 

 other characters, in having the anterior lip of the foot deeply split 

 into two lateral halves. This species has comparatively long, slender, 

 and pointed oral tentacles, and the teeth of its radula are not serru- 

 late — characters which also distinguish it from species of Aldisa. 



29. KosTANGA, Bergh. 



41. ■'^KosTANGA cocciNEA, Forhes (= Archidoris coccinea, 1st Rep., 



p. 178). 



This species is taken so rarely that its habits remain still uncer- 

 tain. Mr. Bourne found a fine specimen, J inch long and -f^ inch 

 broad, on the 1st of August at Drake's Island, low water. It was 

 under a stone resting on black mud with weeds attached, along with 

 Nebalia Geoffroyi. There was no sponge or other red substance near. 

 Cocks, and Alder and Hancock found the species fairly common at 

 Falmouth forty years ago. 



Siih-family — Dokidid^ phanekobeanchiat^, Bergh. 



Goniodorinae. 



30. AcANTHODOEis, Gray. 



42. ■^ACANTHODOBIS PILOSA, MiiU. 



In addition to the previously recorded specimens, one was taken 

 1 Bergh, Oattungen nord. Doriden, Arch. f. Naturgesch., Iv, p. 348, 



