146 Zoological Society. 



teriorly, with a projecting, obtuse, linear tooth, which is divided by 

 a slightly impressed longitudinal groove ; the right margin very nar- 

 row, very thin, and without crest. 



It is possible that this species may prove only a stronger, more 

 robust state of the Nav. tessellata ; nevertheless it differs in its gene- 

 ral form, and its operculum also shows some differential characters. 



7. Navicella tessellata, Lamarck. 



Var. o. T. lateribus angustatd, subrectis ; sub epidermide lutescente 

 lineolis violaceiif seu purpureis creberrimis, et maculis conicis con- 

 centrice seriatis pictd; vertice rectO; luteo ; labia triangulari, antice 

 subarcuato, lateribus prolongato. 

 Var. /3. T. ut in var. a, sed post ice subemarginatd, griseo-fuscd, 

 maculis minoribus luteo-fuscescentihus conicis crehre pictd ; apice 

 dilute purpurascente, recto ; lubio subtriuugulari, ungusto, roseo, 

 antice arcuato. 

 Var. y. ? T. oblong o-ellipticd, antice et postice rotundatd, crassiore 

 sive oblong 0- acuta, lateribus angustatd, nigerrimd, apice eroso ; 

 labio semilanari, interdum triangulari, latiore, subrecto, lateribus 

 non prolongatis. 

 An Nav. Clypeolum, var. } credo, sed ditficile est proband! sine 

 operculo. 



Long. 0-80 ad 0-92 ; lat. 0-76 ad 0-92 ; conv. 0-24 ad 0-48 poll. 

 Hab. Var. a, Cagayan : found in a large river on stones, Var. /^, 

 from Baccara, province of North Ylocos, island of Lu9on : found on 

 stones in a placid river. Var. y. .'' , from Abulug, ])rovince of Cagayan, 

 island of Lu^on : found on stones in a large river. 



Operculum square, a little elongated, narrow, and cut almost 

 square anteriorly, with a slight notch towards the apophysis, which 

 is slightly curved inwards (instead of being straight or turned back- 

 wards, as in that of Nav. chjpeolum) . The inchned angle of the 

 middle of the left side is deeper, and in this species shows a depres- 

 sion or broad canal, in form of a A, the whole length of the apophy- 

 sis ; this canal is limited to the left by two sUghtly raised ribs. 



These characters of the operculum, if they be constant, should 

 suffice to avoid all confusion of this species and the one which pre- 

 cedes. 



8. Navicella lineata, Lamarck. 



Var. o. T. oblongd, postice acuta, luteo-aured, superne lineis spa- 

 diceis radiantibus ex lineolis transversis oburnbratis, antice et late- 

 raliter maculis oblongo-conicis subserialibus pictd ; apice lateraliter 

 compresso, supra foi-nicato, roseo-purpurasceute recto, murginali ; 

 labio angusto-trianguluri, medio concavo-cmarginuto , lateribus an- 

 tice prolongatis. 



Var. /3. T. etlipticd, postice angustatd, luted medio dorsi lineis ni- 

 gris angustis et latiusculis, et lineolis obliquis creberrimis radiis 

 latioribus lateraliter efformantibus interdum conjluentibus pictd, 

 labio triangulari antice arcuato. 



Var. y. T. oblongd, postice angustd, subacutd, luted radiis angustis 

 nigris medio dorsi nolntd, antice et lateraliter crebre nigrescente 



