CONCHOLOGY. 



fore the head ; head and neck dusky ; 

 tentacula four ; lower ones very short ; 

 eyes placed in the tip of the superior 

 pair. 



The application of the Goniometer, 

 upon some commodious construction, 

 might very much facilitate the investiga- 

 tion and determination of species, by 

 ascertaining the precise angle subtended 

 by the two sides of the spire in* uni- 

 valves. This angle combined with the 

 length and breadth of the shell, and pro- 

 portionate 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 

 colour ; whorls five, crossed by nume- 

 rous raised equi -distant acute lines, sepa- 

 rated by regular grooves ; aperture lu- 

 nate, three toothed ; teeth placed trian- 

 gularly, one on the pillar lip situated 

 diagonally ; outer lip, abruptly contract- 

 ing the aperture, 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 f>arva, umbilicata, temiiter stria- 

 ta, Trident, sc. in triangulo positi, nempe 

 wtus ad fwidum oris, niter ad columettam, 

 tertius ad labrum. 



Utter, conch, tab. 92. Jig. 92. 



The three curves formed by the two 

 teeth in the outer lip of this shell bear 

 considerable resemblance to the orna- 

 ment often placed upon pannels in gothic 

 architecture. It is found under the 

 loose moist bark of decaying trees, in 

 some plenty. 



As many of the compound terms as 

 possible ought to be banished from the 

 language of Natural History, we would 

 therefore propose, that the terms miter 

 Up and pillar Up be substituted by Labnim 

 and Labiwn ; these would be equally ex- 

 pressive, and occupy less space in a de- 

 scription, i 



4. H. Jlltemata. Shell somewhat con- 

 vex, fuscus varied or alternating with 

 pale rays ; whorls five, striated across 

 with raised equi -distant acute lines, form- 

 ing grooves between them. Aperture 



thin and brittle ; lip regularly curved, 

 within glossed with perlaceous, and 

 when placed before the light the fuscus 

 lines appear sanguineous. Umbilicus 

 large, exhibiting all the volutions. 



Three-fourths of an inch wide. 



Inhabits the middle states. 



Plate 1. fig. 2. 



H. Radiata Gmetin's Edit, of Syst. Nat. 

 p. 3634. 



Cochlea umbilicata fusca, sive variegata 

 capiUaribus strys leviter exasp> ata. 



Lister, conch, tab. 70. Jig. 69. 



Lister's figure, which is without doubt 

 a representation of this species, is refer- 

 red to in Gmelin as H. radiata, but we 

 believe our shell to be a distinct species 

 from that which is found in France ; we 

 therefore apply a new name. Found 

 under bark of dead trees, and is not un- 

 common. In the young shell the whorls 

 are less rounded, and are flattened above, 

 so as to form almost an angle with the ex- 

 terior margin ; the colours are altogether 

 paler, and may be described as pale yel- 

 low, spotted or above radiate with red- 

 dish-brown, and a row of spots interrupt- 

 ed from the radi by the immaculate pro- 

 minent margin. 



5. H. Glaphyra. Shell very much de- 

 pressed, thin, fragile, pellucid, polished ; 

 whorls five, regularly rounded, and with 

 obsolete and irregular wrinkles across 

 them ; beneath whitish ; umbilicus mode- 

 rate, not exhibiting the volutions. 



Plate 1. fig. 3. 



Taken' by Mr. G. Ord in his garden, 

 Philadelphia. 



It considerably resembles Helix nitens 

 of Europe, particularly in being whitish 

 beneath, and will be properly arranged 

 next that species in the systems. 



GEJ.TS PLAKORBIS. 



Shell discoid simple spiral ; spire de- 

 pressed, flat or sunk; whorls lateral, 

 mouth oblique. 



Observ. The species for which this 

 genus was constructed were included 

 by Linnxus in his Genus Helix. The 

 spire is sometimes profoundly sunk, so 

 much so as to be with difficulty distin- 

 guished from the base. 



1. P. Tri-voltM. Shell sinistral pale 

 yellow, brownish or chesnut colour, sub- 

 carinate above and beneath, particularly 



