TUBICOLARIA.] 



MOLLUSCA. 



117 



Shell thin, brittle, subopaque, transversely subovate, and 

 wedge-shaped when the valves are united ; broad and widely 

 gaping at the anterior side, from whence it gradually decreases 

 until it reaches the opposite extremity, where the valves are 

 closely shut ; anterior termination of the valves with a small 

 but prominent, terminal beak ; external surface covered with a 

 brown or blackish-brown coating, irregularly wrinkled trans- 

 versely ; umbones rather prominent, and obtuse, situate near 

 the larger side, at the junction of the valves on the superior 

 margin ; hinge with an obscure, laminar, transverse tooth in 

 both valves. General length half an inch ; breadth an inch. 



Turton mentions a variety of about half the ordinary size, 

 but not differing in other characters, which is found buried in 

 the back of old oyster shells. 



Inhabits rocks and stones at Torbay, and is an extremely 

 local species. 



Genus 50 — Xylophaga Sowerby. 



Shell nearly orbicular, equivalve, inequilateral, gaping in 

 front, the opening with an angular termination at the back ; 

 two small, somewhat triangular, calyxformed, accessory valves 

 placed over the anterior side of the hinge, and a small tooth 

 lying close to the umbo within each valve, besides an internal 

 rib running from the beak to the basal margin, with a corres- 

 ponding external depression ; anterior muscular impression 

 smallest, situate on the superior margin, close to the beak ; 

 posterior muscular impression large and obovate. 



1. Xylophaga dorsalis, pi. L, f. 8, 9, 10. 



Xylophaga dorsalis, Turton, Biv., p. 16 and 253, pi. 2, f. 4, 

 5 ; Fleming, p. 455 ; Teredo dorsalis, Turton, Conch. Diet., p. 

 185. 



Shell with rounded valves, but destitute of auricles, poste- 

 riorly closed, and provided with an internal rib ; without a 

 reflected, auriform process posteriorly ; the termination plain, 

 and rounded; one valve furnished with a raised, curved process, 

 and a small, slightly cleft one in the other; inside with a joint- 

 ed, longitudinal rib, corresponding to the external groove. 



Found in a piece of wood, at Torbay, by Dr. Turton. 



Genus 51 Dentalium Linnaeus. 



Shell tubular, open at both ends, arcuated, increasing in dia- 

 meter towards the anterior extremity, where the aperture is 

 large and round ; opening of the pointed end very small, and 

 with a lateral fissure in some species ; external surface ribbed, 

 striated, or smooth, but never with annulations. 



1. Dentalium entalis, pi. LVI, f. 7. 



Dentalium entalis, First Ed., pi. 1, f. 7; Pennant, IV, p. 

 145, pi. 90, f. 154; Montagu, p. 494; Donovan, pi. 48; Brown, 

 Conch. Text Book, p. 52, pi. 9, f. 33. 



Tube slightly arcuated, tapering, smooth, and glossy ; fre- 

 quently with inequidistant, circular, irregular wrinkles, or lines 

 of growth ; of a yellowish-white colour. Length an inch and a 

 half; diameter at larger end two-tenths of an inch, smaller end 

 about a twentieth of an inch. 



Inhabits many of the British and Irish coasts. 



2. Dentalium dentalis, pi. LVI, f. 8. 



Dentalium dentalis, First Ed., pi. 1, f. 8; Linnaeus, Syst. 

 Nat., p. 1263, No. 785; Maton and Rackett, p. 237; Montagu, 

 p. 495. 



Tube slender, subarcuated, very taper, terminating in a small 

 point; surface with regular, close-set, longitudinal striae; some- 

 times a few annulations can be traced at the wider end ; colour 

 white, but not glossy. Length half an inch ; diameter at the 

 base half a line. 



Discovered by Colonel Montagu, at Falmouth and south 

 coast of Devonshire, and is a very local species. 



3. Dentalium octangulatum, pi. LVI, f. 2. 



Dentalium striatum, First Ed., pi. 1, f. 2; Dentalium octan- 

 gulatum, Donovan, V, pi. 162 ; Dentalium striatulum, Maton 

 and Rackett, p. 238; Montagu, Sup., p. 155. 



Tube strong, white, arcuated, tapering to a very fine point, 

 and furnished with eight strong, longitudinal ribs, which give 

 to the base, or wider end, an eight-sided appearance ; the 

 nterstices between the ribs are tristriated. Length about two 

 inches. 



A local species, found on the sands at Lelant, Cornwall ; I 

 met with a single specimen at Holy Island. 



4. Dentalium labiatum, pi. LVI, f. 4, 5. 

 Dentalium labiatum, First Ed., pi. 1, f. 4, 5. 



Tube strong, smooth, white, subarcuated, and truncated at 

 the smaller end ; apex closed by a perforated, testaceous lid. 



I found several specimens of this shell in Lough Strangford, 

 Ireland. They are now in the cabinet of Lady Jardine. 



5. Dentalium Gadus, pi. LVI, f. 1. 



Dentalium Gadus, First Ed., pi. 1, f . 1 ; Montagu, p. 496, 

 pi. 14, f. 7 ; Maton and Rackett, p. 238. 



Tube subpellucid, glossy, snow-white, considerably arcuated; 

 contracted towards the larger end, and tapering to a very small 

 point at the other extremity. Length about three-eighths of 

 an inch ; diameter about one-sixteenth. 



Inhabits the British Channel, but is a very rare species. 



2d 



