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LAMELLIBRANCHIATA. | LOWER PALAOZOIC MOLLUSGA. 279 
Position and Locality.—Hard green micaceous Upper Ludlow rock of Tenter Fell, Kirkby Moor, and 
Benson Knot, Kendal, Westmoreland. 
Explanation of Figures.—P\. 1. L. fig. 11. Natural size, left valve ; fig. 11 a, end view. 
LEPTODOMUS IMPRESsUS (Sow. Sp.) 
Syn. and Ref. = Cypricardia? impressa Sow, Sil. Syst. t. 5. f. 3. 
Sp. Ch—Elongate, oblong, compressed, rather more than twice as long as wide; beaks large, broad, close 
to the obliquely subtruncate anterior end, a large, deep, ovate lunette beneath them ; anterior end small, ellipti- 
cally rounded ; posterior end slightly contracted, obliquely truncated; hinge-line long, straight, not elevated ; 
ventral margin nearly straight, with a wide shallow sinus in front of the middle, from which a shallow concavity 
extends obliquely to the beak; posterior slope smooth, obtusely defined; anterior end and sides of the shell 
marked with obtuse, irregular plicze, parallel with the ventral margin. Length one inch four and half lines, 
proportional width from beak to opposite margin ;5,, width of posterior end “, depth of one valve about +. 
This is clearly distinct from either of the varieties of C. amygdalina (Sow.) or C. retusa (Sow.), being as 
long as the former (which see above), and as much depressed as the latter ; agreeing also with the latter in the 
distinctness of the marginal sinus and the depression from it to the beak. 
Position and Locality —Upper Ludlow mudstone of Mortimer’s Cross, Aymestry, Herefordshire. 
Lepropomus TRuNcATUS (M°Coy). Pl. 1. K. figs. 21 to 24. 
Ref.—ld. M°Coy, Ann. Nat. Hist. 2nd Series, Vol. VII. p. 57. 
Sp. Ch.—Oblong or subtrigonal, compressed ; beaks very large, gibbous, prominent, terminal ; the anterior 
end being almost vertically subtruncate under it ; width of the anterior end (where it is greatest) nearly two- 
thirds the length of the shell; posterior end obliquely subtruncate or rounded ; ventral margin gently convex, 
with a searcely perceptible sinus a little behind the vertical line of the beaks; surface ridged with strong, thick, 
irregular wrinkles from the anterior end, becoming obsolete on the posterior slope. Length one inch five lines, 
proportional width from beak to ventral margin ~, depth of one valve about one-third of the width. 
This is somewhat allied to the Cypricardia retusa (Sow.), but has the anterior end even more vertically 
truncate ; it is more elongate (although in this point it varies considerably), but it is most obviously distinguished 
by the strong wrinkling of the surface, parallel with the ventral edges, by which latter, as well as the great depth 
of the truncated anterior end, it also differs from the C. impressa (Sow.). 
Position and Locality—Upper Ludlow, Benson Knot, Kendal, Westmoreland. 
Explanation of Figures —P1|. 1. K. fig. 21. Natural size of average form, right valve; fig. 22, end view 
of both valves, shewing the anterior lunette; fig. 23, remarkably elongate variety ; fig. 24, unusually short 
variety. 
LrePTODOMUS UNDATUS (Sow. Sp.) 
Syn. and Ref. = Cypricardia undata Sow. Sil. Syst. t. 5. f. 4. 
Sp. Ch.—Oblong, very gibbous; beaks large, obtuse; anterior end short, broadly rounded; anterior 
lunette deep, ovate; a strong sinus a little in front of the middle of the ventral margin, from which a deep 
depression extends towards the beak ; surface marked with strong, regular, subequal ridges (four in two lines at 
three lines from the beak), parallel with the ventral margin; strongest on the anterior end, and having one 
upward bend in passing over the sinal depression. 
The specimen before me is small and not sufficiently perfect to give the true measurements, but quite 
enough to shew the species to be perfectly distinct from any of the preceding. 
Position and Locality—Rare in the green quartzose Upper Ludlow rock of Benson Knot, Kendal, West- 
moreland. 
