CONCHOLOGY. 



eyes placed in the tip of the superior 

 pair. 



The application of the Goniometer, up- 

 on some commodious construction, might 

 very much facilitate the investigation and 

 determination of species, by ascertaining 

 the precise angle subtended by the two 

 sides of the spire in univalves. This an- 

 gle 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 

 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 parva, nmbilicata, tenuiter stria- 

 ta, Tridens. sc. in triangulo positi, nempe 

 unus adfundum oris, alter ad columellam, 

 ter-tius 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 orna- 

 ment often placed upon pannels 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 banished from the 

 language of Natural History, we would 

 therefore propose, that the terms outer 

 lip and 'pillar lip be substituted by Labrum 

 and Labium; these would be equally 

 expressive, and occupy le&s space in a de- 

 scription. 



4. //. Jllternata. Shell somewhat con- 

 vex, fuscus varied or alternating with pale 

 rays ; whorls five, striated across with 

 raised equi-distant acute lines, forming 

 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. 



Plat el. fig. 2. 



U. Kadiata Gmelin'a Edit, of Sgst. Nat. 

 p. 3634. 



Cochlea umbilicata fused, sive -variegata 

 capillaribus strys leviter exasperata. Lister. 

 Conch, tab. 7Q,Jig. 69. 



Lister's figure, which is without doubt 

 a representation of this species, is refer- 

 red to in Gmelin as U. radiata, but we be- 

 lieve our shell to be a distinct species 

 from that which is found in France ; we 

 therefore apply a new name. Found un- 

 der bark of dead trees, and in moist places, 

 and is not uncommon. In the young 

 shell the whorls are less rounded, and 

 are flattened above, so as to form almost 

 an angle with the exterior margin ; the 

 colours are altogether paler, and may 

 be described as pale yellow, spotted or 

 above radiate with reddish-brown, and 

 a row of spots interrupted from the 

 radii by the immaculate prominent margin. 



5. //. Glaphyra. Shell very much de- 

 pressed, thin, fragile, pellucid, polish- 

 ed ; whorls five, regularly rounded, and 

 with obsolete and irregular wrinkles 

 across them ; beneath whitish ; umbili- 

 cus moderate, not exhibiting the volu- 

 tions. 



Plate 1. fig. 3. 



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

 Philadelphia. 



This species and the preceding are re- 

 ferable to the genus Zonitis, Montf. a 

 name which is objectionable from its be- 

 ing used in Entomology. 



It considerably resembles Helix nitens 

 of Europe, particularly in being whitish 

 beneath, and will be properly arranged 

 next that species in the systems. 



6. H. thyroidus. Shell thin, fragile, con- 

 vex, umbilicate ; whorls five, obtusely 

 wrinkled, or rather with equi-distant, 

 gradually elevated, obtuse lines, and spi- 

 rally striate with minute, impressed lines ; 

 lip widely reflected, white and flat before, 

 partially concealing the umbilicus ; 

 pillar lip furnished with a very oblique 

 tooth. 



Journal of the Jicad. of Nat. Sciences, 

 vol. i. p. 123. 



Breadth four-fifths to nine-tenths of an 

 inch. 



This species very much resembles H. 



Albolabns, but is umbilicated, and toothed 



on the pillar lip. It is much less common. 



It is referable to the genus Cepofis, Montf 



