TRITONIA. 583 



with scalloped margins. This fine species grows to half a 

 foot, and even more, in length. 



It occurs on both our east and west coasts, but is scarce. 

 The largest specimens we have met with were taken on the 

 scallop banks, in twenty-five fathoms water, off the north 

 coast of the Isle of Man. 



2. T. PLEBEiA, Johnston. 



Tritonia plebeia, Johnston, in Edinb. New Phil. Journal, vol. v. p. 77, and 

 Ann. Nat. Hist. vol. i. p. 115, pi. 3, f. 3, 4. — Alder and 

 Hancock, Monog. part 3, fam. 2, plate 3. 

 „ pulchra (vAR.) Johnston, Edin. New Phil. Jour. vol. v. p. 78. 



Body (an inch or more in length) lanceolate, quadri- 

 lateral, with subparallel sides for a great part of its length, 

 truncate in front, tapering behind, yellow or yellowish- 

 brown, with brown markings, and often opaque white 

 specks. Margins of the back not waved, edged by five or 

 six (on each side) branchial tufts, which are distant, small, 

 erect, pinnate and insequilateral. Head veil entire, scal- 

 loped, edged by six simple tentacular points. Dorsal 

 tentacles issuing from entire-edged cylindrical sheaths ; 

 they terminate in a fasciculus of simple filaments. 



Very generally distributed in the British seas. It in- 

 habits the coralline zone, and lives upon zoophytes. 



3. T. LiNEATA, Alder and Hancock. 



Ann. Nat. Hist. 2nd series, vol. i. p. 191, and Monog. part 5, fam. 2, 

 plate 4. 



Body (less than an inch in length) very slender, linear, 

 quadrilateral, pellucid white with an opaque white line 

 along each simple margin of the back. Branchise slender, 

 white, imperfectly bipinnate, arranged distinctly four or 

 five on each side. Head veil produced in front into four 



