238 CLASS III. GASTEROPODA. ORDER VII. PECTINIBRANCHIATA. 
in the columella being truncated. Deshayes places them, on account of 
this last-mentioned peculiarity, with the Melanopsides, but the difference 
in the habits of those mollusks 1s alone sufficient to determine the impro- 
priety of their being associated together. The learned author of the 
‘Manuel de Malacologie’ likewise attaches but little importance to the 
difference in the habits of mollusks as affecting their classification ; we 
fully estimate his method of referring the Planaxes to his family of the 
Entomostomata in approximation to the Buccina, but not of removing the 
Melanopsides with them. 
The shell of Planaxis may be described as being solid, ovately-conical, 
and notched at the base with a very narrow sinus ; the aperture is ovately- 
oblong ; the columella is smooth, depressed towards the base, and trun- 
cated, and it has always a wide callosity at the upper part; the outer lip 
is for the most part thickened, and the interior of the shell is either sul- 
cated or lined. 
Examples. 
PIICCLXX. Figs. 
Pianaxis sutcatus, Lamarck, Anim. sans vert., vol. vii. p. 51. Lister, 
Historia Conchyliorum, pl. 980. f. 39. 
Buccinum sulcatum, Bruguiére. 
Pl. CCLXX. Fig. 2. 
PLANAXIS MOLLIS, Sowerby, Genera of Shells, No. 12. 
Pl. CCLXX. Fig. 3. 
PLANAXIs SEMISULCATUS, Sowerby, Genera of Shells, No. 12. 
EBURNA, Lamarck. 
Testa oblongo-ovata, spira acuminata, anfractibus plus minusvé convexis, 
suturis plus minusve canaliculatis ; anfractu ultimo canali brevissimo 
terminato, umbilicum amplum formante ; apertura subovali; colu- 
