13 



111 in as a film, more especially towards the anterior part. 

 Yet even in its very immature state, the tube of this species 

 has near the tail, some distinct testaceous chambers : showing 

 the fact that the body makes some progress beyond simple 

 growth : a circumstance less clearly established in the com- 

 mon Auger Worm. The chief, or at least, the most clear 

 and easy distinction between this species and T. Navalis will 

 be found in the structure of their jaws: the cutting portion 

 of which, or triangular projection, in the latter species being 

 bent obliquely downward, but not nearly so much so as in 

 T. Malleolus, In T. Navalis, fine, slight, closely placed 

 lines radiate backward from this point to where the upper 

 portion of them joins a series of similar striae that pass upward 

 in an arched manner, each line turning off backward into a 

 flat space which ends abruptly. The jaws of T. Malleolus 

 are more glossy, and the divergent lines of the triangular 

 portion are less numerous and more distinctly separate ; the 

 striae being more prominent, with wider spaces between them. 

 The perpendicular lines also, which run at right angles to 

 the former, are also more distinct, though examined in a 

 much smaller specimen; and turn off backward in separate, 

 but not as in the former, in wide arches. 



T. NANA. Flem. Brit. An., p. 455 ; whose sole authority 

 is Turton. The shell is four tenths of an inch in diameter, 

 in both directions, though too irregular to be termed 

 round ; very deep in the hollow, almost globular. A 

 slender, but very distinct rib passes round the concavity, 

 from the slight but firm oblique tooth at the portion that is 

 incurved, to the opposite margin. This rare species was 

 found in a piece of oak, thrown on shore at Gorran : com* 

 munieated by Mr. Peach. 



PHOLADARIA. 

 Shell without a tubular sheath, gaping anteriorly ; ligament 

 external, and with accessory pieces of shell not belonging 

 to the valves. 



PHOLAS. 



GENERIC CHARACTER: Shell bivalve, equal valved, 

 transverse, gaping at both sides, having accessary pieces 

 affixed above or below the hinge. The inferior or pos- 

 terior margin of the valves reflected outward. 



P. DACTYL US. Turt. Lin. Borlase's Nat. Hist. Corn., 

 p). 28, fig. 31. Pen. Brit. Zo., vol. 4, pi. 39, fig. 10. 

 Mont. Test. Brit., vol. 1, p. 20. Flem. Brit. An., p. 457. 

 This shell is a borer, commonly of the hard rock, in which 

 it lives at ease, and by which it is protected from injury. 

 1 have only seen it as taken from slate rock on the west 

 sidtf of Pridmouth Cove, not far west of Fowev. 



