PLEUROBRANCHUS. 199 



Shell subopaque, pellucid, elongated, straight-sided, lightly 

 rounded in front, the dorsal margin suddenly reflexed and winged! 

 behind ; right back margin obtusely angled ; whorls 2, spire mamil- 

 late, prominent ; suture impressed toward the aperture, margin in- 

 cised ; submembranous growth-striae regular, growth-sulci remote, 

 interstices iridescent with frequent splendid dots; radial striae very 

 obsolete, radial impression sublateral ; length 5, width 3 mill. 



St. Thomas, West Indies on corals in 3-4 ft. (Riise) ; also Guade- 

 loupe. 



Pleurobranchus voisin du Pleurobranche orangeDESH., Journ. de 

 Conch., 1857, p. 142. ? Pleurobranchus sp., RANG, Manuel, pi. iii r 

 f. 4. Berthella quadridens MORCH, Journ. de Conch., 1863, p. 29. 



The number of leaflets on gill is more numerous than in PL 

 aurantiacus Risso, and the two species are readily distinguished by 

 the lingual teeth. In P. quadridens there are three denticulations 

 on the recurved cusp, the two lower being smaller and equal, while 

 in P. aurantiacus there are ten little and nearly equal digitations at 

 the point. 



Morch's reference to Rang for an illustration, is only one of hi& 

 jests. See also Haliotinella patinaria Guppy. 



P. AREOLATUS Morch. 



Body soft, nearly prismatic, suboval, gibbous from contraction ; 

 mantle suboval, rectangularly emarginate in front, back areolate, 

 the areas oblong-hexagons, central ones rather smooth, those at 

 sides smaller with a median wart, anterior marginal areas small, ob- 

 solete, but with very distinct papillae. Foot oval, the margin thin, 

 undulated, anterior sulcus of foot gaping, laterally much reduced, 

 sole narrowed behind, with a longitudinal sulcus glandulose on each 

 side nearly one-third the length of foot. Veil above the mouth 

 transverse, narrow, with subacute, slit lateral angles, the bases of 

 the sides reticulated with small confluent purple spots. Tentacles 

 with circular sulci, approximate, cylindrical, rolled, slit down the 

 side and perforate at apices. Eyes large and black, midway be- 

 tween bases of tentacles and the mantle. Gill plume long, triangu- 

 lar, the sides subparallel, with about 16 alternating secondary 

 plumes on each side, becoming smaller toward the apex, each with 

 a strong wart at the base. Length 21, width 16, alt. 15 mill, in the 

 contracted condition. 



