68 TRITONIID^. 



(Loven).] It is the Tritonia atrofusca of Macgillivray ; and 

 his genus Sphcerostoma was founded on an imperfect specimen 

 of the present species. 



2. T. alba, Alder and Hancock. 

 T. alba, A. & H. Brit. Nud. Moll. p. 46, and App. p. vi. 



Body rather depressed, transparent-white, with opaque-white 

 transverse markings, smooth or very slightly tuberculated : 

 head-veil bilobed, with irregular digitations : tentacles with 

 slightly branched filaments, retractile within rather wide 

 sheaths with smooth edges : branchial processes imperfectly 

 bipinnate, on each side 4 or 5, with intermediate smaller ones, 

 set on an expanded and waved pallial margin : foot moderately 

 broad. L. 0-75. 



Habitat : From the fishing-boats at Cullercoats ; rare 

 (Alder). 



3. T. plebeia, Johnston. 



T. pleheia, Johnst. in Edinb. New Phil. Journ. v. p. 77 ; A. & IL Brit. 

 Nud. Moll. fam. 2, pi. 3. 



Body subquadrate, yellowish (or rarely greenish), with brown 

 markings on the sides of the back, which are interrupted oppo- 

 site to each branchial tuft; sides of the body generally marbled 

 with purple-brown : head-veil nearly entire, with from 6 to 8 

 digitations : tentacles smooth and transparent below, above 

 fasciculated with slender branched filaments ; they issue from 

 small sheaths with smooth margins : branchial processes small, 

 bipinnate, about 5 or 6 on each side, with sometimes smaller 

 intermediate ones, set on a very slight pallial ridge: foot 

 narrow, rounded in front. L. 1. 



Habitat : On Alcyonium digitatum and other zoophytes 

 in the laminarian zone ; frequent, especially on the east coast. 

 [W. Sweden (Loven) ; JEgean, 25 f. (Forbes).] 



4. T. lineata, Alder and Hancock. 



T. lineata, A. & H. in Ann. N. H. 2nd ser. i. p. 191 ; Brit. Nud. Moll. 

 fam. 2, pi. 4. 



Body very slender, subquadrate, transparent-white, with a 



