98 



CONCHOLOGY. 



Bivalves. 



Distortus, 



Obsoletus, 



Glaber, 



Lucvis, 



S.milis, 



Tragi lis, 



Subauricu- 

 lata. 



X LI V. 



OSTKEA. 



eqiial ; length an inch and a half, breadth not quite so 

 much, 



Brit. Shells, tab. 116. 

 Found on several places on the English coast. 



6. Distortus. Shell distorted, with numerous rib- 

 like striae ; upper valve flattened, the under valve irre- 

 gular ; young shells with concave short spines on the 

 ribs ; length two inches, breadth two inches and a half. 



Brit. Zool. tab. 61. fig. 65. 

 Brit. Shells, tab. 34. 

 Wallace's Orkney, p. 44. tab. 1. 

 Found on several places on the English coast; it 

 likewise occurs in Orkney and Zetland. 



7. Obsoletus. Shell with numerous fine longitudinal 

 stria?; eight or ten of these more prominent than others, 

 at irregular distances; sometimes smooth; valves equal, 

 rather flat; auricles unequal, one very large, striated, the 

 other extremely small ; white shell, with minute decus- 

 sating striae, giving the shell a shagreen appearance. 



Lin. Trans, vol. viii. tab. 3. fig. 5. 

 On the English and Scottish shores frequent. 



8. Glaber. Shell with seven rounded rays, not much 

 elevated, with longitudinal striae ; and ears nearly 

 equal and large, one of them reticulated, the other stria- 

 ted; inside marked with twenty-one slender rays, mid- 

 dle oues in fours : length three quarters of an inch. 



Test. Brit. tab. 28, fig. 6. 

 Found in Anglesea by Mr Pennant, and on the Scot- 

 tish coast. 



9. Lcevis. Shell smooth glossy, slightly wrinkled 

 concentrically ; colour whitish ; one ear very large, the 

 other small and slightly striated longitudinally ; diame- 

 ter about half an inch. 



Test. Brit. p. 61. Sup. 

 Found by Mr Montagu in Falmouth harbour. Pen- 

 nant marks his shell from Anglesea. 



10. Similis Shell thin, semitransparent, smooth, 

 beautifully clouded with brown, of a compressed glo- 

 bose form, with unequal ears. 



Mem. Wer. Soc vol. i. tab. 8. fig. 8. 

 Found by Mr Laskey in the Frith of Forth. 



1 1 . Fragilis. Shell subovate, oblong, convex, fra- 

 gile, sub-pellucid, white, wrought with numerous slight- 

 ly undulated longitudinal striae, with two or three mi- 

 nutely fine intermediate ones ; valves equal inequilate- 

 ral, one side straight, the other arcuated ; auricles 

 equal small ; hinge a little oblique ; length three quar- 

 ters of an inch, breadth scarcely half an inch. 



Test. Brit. p. 62. Sup. 



Found by Mr Montagu on the coast of Devon, in- 

 termixed with serliilaricE. 



12. Subauriculata. Shell ovate, oblong, pellucid, 

 white, equilateral, equivalve, with small equal angu- 

 lar projections or auricles, wrought with numerous 

 longitudinal striae that slightly crenate the margin; 

 along the middle are two stria?, that appear more con- 

 spicuous than the rest, by being opake, and are equal- 

 ly evident on the inside ; length a quarter of an inch, 

 breadth half its length. 



Test. Brit. tab. 29. fig. 2. 



Found by Mr Montagu with the preceding species, 

 and we have found it in Zetland. 



Genus XLIV. Ostrea. 



Shell adhering, inequivalve ; hinge toothless, with a 

 cardinal oblong transversely striated cavity, to which the 

 ligament is attached ; one muscular impression in each 

 valve 



1. Edulis. Shell sub-orbicular, ragged, with imbri- Bivaivi 

 cated membranaceous folds. v ~" ~v 



Brit. Zool. tab. 62. fig. 70. inf. Edulis ' 



The common oyster. Found on many of the Bri- 

 tish shores. A variety occurs in Salcomb Bay, Devon- 

 shire, very thin, with membranaceous plates wrinkled 

 into irregular interrupted ribs ; upper valve flat, or rather 

 concave on the top, with a corneus margin, half an inch 

 broad. It is called by the fishermen Rock Oyster. 



Genus 'XL V. Anomia. 



Shell irregular, one valve flattened, with a perforation XLV. 

 near the hinge, through which the animal is immovcably Anomia. 

 fixed by a testaceous operculum to some other body; hi,ige 

 a transverse linear prominence on the flat valve connected 

 under the beak of the opposite valve by a strong cartilage. 



1. Ephippium. Shell sub-orbicular, irregularly wrink- Ephip- 

 led, waved, and sinuous ; one valve convex, the other pium, 

 flat and perforated, adhering to oysters and other bo- 

 dies, and taking the impression of their form ; inside 

 pearlaceous, glossed with green; diameter sometimes 

 three inches and a half. 



Brit Zvd. tab. 6'2. sup. fig. 



Brit. Shed*, tab. 26. 



Test. Mm. liar. tab. 3. fig. 20. young. 

 This shell is common, adhering to marine bodies. 

 In its young state, it is more thin and membranaceous, 

 and has been termed A. squumula. 



2. Acideata. Shell thin, compressed, muricated, with Aculeafa 

 interrupted longitudinal strife, furnished with small 

 concave spines ; beak small, turning a little down- 

 wards ; under valve flat, generally plain, sometimes a 



little echinated towards the margin, and perforated 

 near the hinge ; length nearly half an inch. 

 Test. Brit. tab. 4. fig. 5. 

 Common on the roots of ah ce, from the Zetland Islands 

 to Cornwall. 



3. Undulata. Shell sub-orbicular, marked with fine, undulata 

 irregular, undulated, longitudinal, rib-like striae ; beak 



very small, placed near the top, a little surrounded by 

 the margin ; under valve flat, perforated ; diameter an 

 inch and a half. 



Brit. Shells, tab. 45. Ostrea striata. 

 Common in the same situations as the A. ephippium. 



4. Cymbiformis. Shell sub-ovate, lengthened, sub- 

 pellucid, white ; the upper valve considerably convex, 

 contracting at the umbo, with a beak incurved upon 

 the other valve • slightly wrinkled transversely ; lower 

 valve conforms to the shape of the body, to which it is 

 attached; length about three-tenths, breadth two-tenths. 



Lin. Trans, vol. viii. tab. '?. fig. 6. 



Found by Mr M f Leay on the coast of Caithness. 

 Mr Montagu has found it in Devonshire; and Mr 

 Laskey in the Frith of Forth. ' We have observed it on 

 the spines of Echinus Cidaris from the coast of Zet- 

 land. 



A shell occurs frequently at Newhaven, near Edin- 

 burgh, in the oyster boats, which we suspect will con- 

 stitute a new species of this genus, which may be term- 

 ed fusca. Only the convex valves have occurred, 

 These are nearly orbicular, moderately convex, closely 

 covered with small tubercles, or plain, with a few trans- 

 verse waved lines ; opake, of a light brown colour, and 

 glossy within ; diameter four-tenths. 



SECT. II. EQUIVALVE. 



The shells of this Section are more regular in their 



Cymbifor- 



