CONCHOLOGY. 



67 



Univalve. 3. Strialulwn. Shell tapering, subarcuated, with 

 V ~""V~' eight ribs or angles, and intermediate striae. 

 Stnatulum. Don Bri( SkMS} teb lg2 D Octangulatum. 



Found on the sandy coast of Cornwall, near Lelund, 

 by Miss Pocock. 

 Gadus. 4. Gadus. Subarcuated, tapering, smooth, white, 



contracting a little toward the larger end ; length about 

 three-eighths of an inch. 



Test. Brit. p. 496. tab. 14. fig. 7- 

 First described by Montagu, who says that it is found 

 in many parts of the British channel, and known to ma- 

 riners by the name of Hake's-tooth, 



Genus V. Cecum. 



V. C«cum. Shell tubular, subcylindrical, subarcuated, undivided, 

 and closed at the apex. 



Obs. None of the shells of this genus were known 

 to Linnaeus. Mr Boys discovered the C. Imperforatum, 

 which was inserted by Mr Walker in the genus Denta- 

 lium, without sufficient consideration, as one of the cha- 

 racters of that genus, " ulraque extremitate perviu," for- 

 bade its admission. The impervious apex, and cylin- 

 drical form of the Imperforatum, and two others lately 

 discovered, point out the propriety of constituting a 

 new genus for their reception, 

 pcrfora- 1. Imperforatum. Shell cylindric, subarcuated, stria- 

 ], ted transversely ; aperture a little contracted at the mar- 



gin ; apex truncated, and furnished with a small round 

 protuberance ; length one-eighth of an inch, breadth 

 one-third of its length. 



Walker's Minute Shells, fig. 15. Dentalium. 

 Found by Mr Boys at Sandwich, and by Mr Monta- 

 gu at Falmouth, 

 ichea, 2. Trachea. Subcylindric, subarcuated, with regu- 



lar, strong, transverse striae; aperture round; apex 

 truncated, and furnished with a small round protube- 

 rance ; length about one-eighth of an inch, the dia- 

 meter about one-fifth of its length. 



Test. Brit. p. 497. tab. 14. fig. 10. Dentalium 

 Trachea. 

 Discovered by Mr Montagu in sand from Milton, De- 

 vonshire. 

 51abrum. 3. Glabrum. Shell cylindric, arcuated, smooth, glos- 

 sy; mouth orbicular; apex rounded and submarginated ; 

 length one line. 



Test. Brit. p. 497. Dentalium glabrum. 

 Discovered by Mr Montagu in Biddeford Bay, and 

 at Barnstable, Devonshire ; Capt. Laskey has observed 

 it at Dunbar ; and we have found it in Zetland 



Genus VI. Serpula. 



fl. Serpu- Shell tubular, Jlexuous, contorted, adhering to other 

 .a. bodies. 



Obs. The inhabitants of this genus of shells belong 

 to the class Annelides of Latreille, and may with pro- 

 priety be divided into several genera. Their history is 

 still involved in much obscurity. 

 {erm ; cula- l. Vermicular is. Shell round, opake, flexuous, ta- 

 pering to a fine point, wrinkled transversely, and at- 

 tached throughout its whole length to other bodies. 

 Diameter sometimes as large as a swan's quill ; length 

 from three to four inches. 



Bril.Zool tab. 91. fig. 158. 

 Pult. IIugIi. Dorset, tab. 22. fig. 9. 

 This is a common shell, adhering to stones, old shells, 



and corals. It is subject to considerable variation in its Vnlvi lv« 

 shape. The Serpula Intricata of Linnaeus may be re- **Y" afc " 

 ferred to this species. 



The annimal resembles a Terebella. It is furnished 

 with branched ciliated tentacula, which are spotted 

 with crimson* and when extended, almost surround a 

 double funnel-shaped proboscis. 



2. Triquetra. Shell strong, white, opake, contorted, Triquetra, 

 wrinkled transversely, base spreading, back furnished 



with a keel or ridge. Diameter one-tenth of an inch. 

 Brit. Zool. tab. 91. fig. 157. S. Contortuplicata. 

 Brit. Shells, tab. 95. S. Vermicularis, exclusive 

 of the middle and right hand figures. 



This shell is very common, adhering to shells and 

 stones, or twisted round the stalks of fuci. It varies 

 much in shape, being sometimes nearly destitute of any- 

 dorsal ridge, and occasionally furnished with two small 

 lateral ridges. 



The inhabitant, as described by Mr Montagu, and 

 figured by Ellis, {Corallines, tab. 38. fig. 2.), pos- 

 sesses two tentacula, which are plumose, or furnished 

 with numerous ciliated fibres, varying in colour, being 

 barred with blue, yellow, brown, or red. The trum- 

 pet-shaped proboscis is finely striated, and the margin 

 crenated. 



Mr Montagu likewise found four other animals inha- 

 biting shells of similar form, as the triquetra, yet dif- 

 ferent from the one which is now described. 1 . With 

 a smooth and slightly concave testaceous termination 

 or operculum. 2. With a testaceous termination, arm- 

 ed with two or three spines in front. 3. With a testa- 

 ceous conical termination. 4. With a smooth termina- 

 tion, grooved on each side for the reception of two cirri 

 placed at the base of the operculum, which is corne- 

 ous, and furnished with a bifid stile. 



3. Serrulata. Shell transparent, smooth, glossy, tri- Serrulata, 

 angular, tapering, flexuous, base spreading, adhering ; 



dorsal ridge serrated, and a little produced at the open- 

 ing. Breadth at the base two-tenths of an inch, length 

 about three inches. 



This new species was found in Zetland in 1 809, ad- 

 hering to stones brought from deep water, to which it 

 is attached throughout. Its transparency and lustre, 

 independent of other characters, entitle it to a separate 

 place in the system. 



4. Tubularia. Shell white, opake, round, tapering, x u bularia 

 slightly wrinkled transversely, adhering af the smal- 

 ler end, and irregulai'ly flexuous. Diameter two-tenths 



of an inch, length seven inches. 

 Test. Brit. p. 513. 



It was first observed at Torcross, Devonshire, by Mr 

 Montagu. It is found in Zetland, along with the pre- 

 ceding species. 



Mr Montagu observes, that the animal is an amphi- 

 trite, with between fifty and sixty annulations. The 

 head is long, white, and barred with green, having a 

 loose scalloped dilatable membrane on each side. Ten- 

 tacula two, beautifully feathered, each originating from 

 a single stalk, and placed near to each other, on the fore- 

 part of the head. 



Family III. FLASK-SHAPED. 



The shells included in this family were unknown 

 to Linnaeus. They are furnished with a one-celled ca- 

 vity, are destitute of a spire, and in shape resemble a 

 bottle or flask. The family contains only one genus, 

 which is denominated Lasena. 



