by the two sides of the spire in univalves. This angle, combined 

 ■with the length and breadth of the shell, and proportionate length 

 of the mouth, would, it is conceived, give us a better idea of form 

 than we can have by the present mode of description. It is a plan 

 we have adopted in describing our marine shells. 



3. H. TRIDENTATA. — Shell depressed, spire very little raised, 

 brownish or horn color ; whorls five, crossed by numerous raised, 

 equidistant, acute lines, separated by regular grooves ; aperture 

 lunate, three toothed ; teeth placed triangularly, one on the pillar 

 lip situated diagonally ; outer lip abruptly contracting the aper- 

 ture, widely reflected and white, furnished with two of the teeth 

 resembling projecting angles. Umbilicus moderate. 



Half an inch wide. Inhabits the Middle States. Plate 2, fig. 1. 



Cochlea parva, umbilicata, tenuiter striata. Tridens sc. in 

 triangulo positi, nempe unus ad fundum oris, alter ad columellam, 

 tertius ad labrum. Lister, Conch, tab. 92, fig. 92. 



The three curves formed by the two teeth in the outer lip of 

 this shell bear considerable resemblance to the ornament often 

 placed upon panels in Gothic architecture. It is found under the 

 loose moist bark of decaying trees in some plenty. Belongs to the 

 genus Polydontes, Montf. 



As many of the compound terms as possible ought to be ban- 

 ished from the language of Natural History, we would therefore 

 propose that the term ow^er-lip and pillar-li^ be substituted by 

 Labrum and Labrum; these would be equally expressive, and 

 occupy less space in a description. 



4. H. ALTERNATA. — Shell somewhat convex, fuscous, varied or 

 alternating with pale rays ; whorls five, striated across with raised 

 equidistant acute lines, forming grooves between them. Aper- 

 ture thin and brittle ; lip regularly curved, within glossed with 

 perlaceous, and when placed before the light, the fuscous lines 

 appear sanguineous. Umbilicus large, exhibiting all the volutions. 



Three-fourths of an inch wide. Inhabits the Mddle States. 

 Plate 1, fig. 2. 



H. radiata, Gmelin's Ed. of Syst. Nat. p. 3634. 



Cochlea umbilicata, fusca, sive variegata, capillaribus stryis 

 leviter exasperata. List. Conch, tab. 70, fig. 69. 



Lister's figure, which is, without doubt, a representation of this 

 species, is referred to in Gmelin as //. Rndiaia, but we believo 



