100 



CONCHOLOGY. 



Bivalve! 1 



XLVII. 

 Finn*. 



l'ectinata, 



lngens, 



Genus XLVII. Pinna. 



Shell longitudinal, cuneiform, with an acute base; valve 

 gaping in the upper pari ; hinge without teeth, extend- 

 ing nearly the whole length of the shell; affixed by a 

 byssus. 



1. Pectinata. Shell pellucid, thin, brittle, marked 

 with about eleven longitudinal striae or ribs from the 

 apex to the opposite margin, furnished with concave 

 spines ; about one-third of the shell opposite the hinge 

 without ribs ; breadth three inches at the gaping end, 

 length six inches and a half, tapering to the apex. 



Brit. Shells, tab. 10. P. muricata. 

 Found on the English coast, but not common. 



2. In gens. Shell rugged, with irregular concentric 

 wrinkles running lengthwise from the beak to the open 



side, sometimes breaking into lamina* ; hinge straight, 

 turning a little inwards at the apex ; on the under side, 

 opposite the beak, concave ; length about a foot, breadth 

 seven inches. 



Brit. Shells, tab. 152. 



Found in Shetland, where they are frequently fished 

 up on the hook by the cod-fihers. Mr Montagu has 

 likewise found them in Salcomb bay, Devonshire. 



3. Muricata. Shell thin, brittle, semi-pellucid, flesh- 

 coloured, darkest at the smaller end, with ten or twelve 

 broad ribs running longitudinally the whole length, and 

 a few intermediate smaller ones at the narrow end ; be- 

 set sparingly with concave prickles towards the larger 

 end, principally towards the extremity ; length five in- 

 ches, breadth three inches. 



Test. Brit. tab. 5. fig. 3. 



Found near Weymouth, Dorset, by Dr Pulteney. 



Bivalves, 



Muricata. 



ORDER III. MULTIVALVES. 



XL VIII. 



Pholas. 



Dattylus, 



Multi- This order of shells was proposed by Major, under 



valves the title Pluvalvia. It includes such testaceous bo- 

 — ""Y"™*' dies as are composed of more pieces than two. It is 

 by no means a natural division ; and hence will only 

 be employed in an artificial system. This order ad- 

 mits of two divisions. 



DIVISION I. DENTATED. 



In this division we include two genera, which differ 

 widely from each other in external aspect, although 

 they have many points of resemblance in structure and 

 economy. 



Genus XLVIII. Pholas. 



Shell transverse, composed of two principal valves, open 

 at each end, with small accessory pieces placed on the li- 

 gament, or at the hinge; hinge recurved, united by a 

 cartilage., beneath which is an uncurved tooth. 



1 . Dactylus. Shell striated transversely, and slightly 

 longitudinally ; the interior end strongly muricated, ex- 

 tending into a beak and forming a large gape ; teeth, one 

 in each valve, projecting inwards, long, curved, flat ; 

 the smaller valves are four in number ; length an inch 

 and a quarter, breadth four inches. 

 Brit. Zool. tab. 39. fig. 10. 

 Brit. Shells, tab. 118. 

 This shell is very common on the British shores, be- 

 ing found in marl, clay, and wood. 

 Parvus, 2. Parvus. Shell white, rough, longitudinally and 



transversely striated except at the smaller end; the 

 larger end declines into a kind of muricated beak ; 

 hinge reflected, without cells ; one plate at the back 

 connected by a membrane to the valves ; teeth one in 

 each valve, slender, curved, with a knob at the base ; 

 length half an inch, breadth one inch. 

 Brit. Zool. tab. 4. fig. 13. 

 Test. Brit. tab. 1. fig. 7, 8. 

 This shell was first described by Pennant. It has 

 been found also by Mr Montagu at Salcomb on the coast 

 of South Devon. 

 Crispatus 3. Crispatus. Shell opake, strong, gibbous, suboval, 



obtuse, and open at both ends,- transversely striated ; 

 half the shell reticulated, and separated from the plain 

 side by a broad furrow down the middle, extending 

 from the beak to the opposite .margin ; hinge reflected, 

 emooth, forming a cavity at the anterior end, which is 



obliquely truncated to the front margin; teeth two, long, 

 flat, curved ; length about two inches, breadth three. 



Brit. Zool. tab. 40. fig. 12. 



Brit. Shells, tab. 62. 

 On the English and Scottish shores frequent. 



4. Candidas. Shell thin, whitish, rounded at both Csndidus, 

 ends, and closed at the larger end ; striated transversely, 



and crossed by finer striae radiating from the beak ; a 

 few of the radii at the larger end muricated ; tooth in 

 each valve slender incurvated, above which, on the mar- 

 gin of one valve, is an erect toothlike process; length 

 seven-eighths of an inch, breadth two inches and a half. 



Brit. Zool tab. 39. fig. 11. 



Brit. Shells, tab. 132. 

 Found on the British shores, but not common. 



5. Striatus. Shell white, conoid, the larger end Siriatu*. 

 strongly reticulated, the rest irregularly striated ; at the 



front margin the lip seems to fold back, and forms a 

 smooth surface on the reticulated part; hinge plate 

 large and suboval ; teeth long, slender, and much cur- 

 ved ; length half an inch, breadth three quarters. 

 Brit. Shells, tab. 117- 

 Frequent in tli£ bottoms of ships. It is not ascer- 

 tained whether it breeds in our seas. 



Genus XLIX. Teredo. 



Shell with two principal hemispheric valves, truncated XLIX. 

 and open at the end, and two small lanceolate accessory Teredoi 

 valves remote ; hinge ivith a long incurvated tooth in each 

 valve ; tube testaceous, sub-cylindric, Jlexuous, in which 

 the animal resides but to which it is not attached. 



Obs. This genus was placed in the order Multivalves 

 by Adanson. It was removed by Linnaeus into the 

 order Univalves. Its title to its former situation is now 

 placed beyond a dovibt, by the interesting observations- 

 of Mr Montagu and Mr Home. 



1. Navalis. Tube thin, brittle, flexuous, of a whitish Naval5s 

 colour, lodged in wood ; valves white, each furnished 

 with a long flat curved tooth, projecting inwards under 

 the hinge, and a short lateral tooth at the extremity of 

 the hinge. 



Brit. Shells, tab. 145. 



Phil. Trans, part. 2. tab. 12.. 13. 



This shell, called by Linnaeus calamitas navium, is 

 found in planks and stakes which have lain in the sea. 

 It often pierces the planks of ships, particularly in 

 warm climates, and soon effectually destroys thetn. 



