286 BRITISH PALAXOZOIC FOSSILS. [ LaAMELLIBRANCHIATA. 
Explanation of Figures —P\. 1. K. fig. 4, natural size of elongate variety; fig. 5, shorter variety ; 
fig. 5a, do. magnified to shew the hinge-teeth and muscular impressions. 
NUCULITES posT-sTRIATUS (Hmmons). PI. 1. K. fig. 6. 
Ref—Geol. Rep., and Hall, Pal. N. Y. t. 34. f. 2, and t. 82. f. 10. 
Sp. Ch.—Ovato-rhomboidal ; beaks small, pointed, compressed ; anterior end short, broadly rounded, the 
curve passing into that of the convex ventral margin; posterior end narrowed, obliquely truncated; a 
sharp angular ridge extends from the beak to the respiratory angle, defining the flattened posterior slope; sides 
gently convex, most so a little in front of the middle of the diagonal ridge ; posterior slope marked with strong, 
subequal, radiating ridges, six or seven in the space of one line. Length nine and half lines; in proportion to 
length, greatest width (from middle of ventral margin to opposite hinge-line) >, length of anterior side ¥ 
100 9 
depth of one valve =. 
As neither the American geologists nor myself have seen any trace of hinge-line, the genus is very 
doubtful. 
Position and Locality —In the calcareous schists of Gwyddelwern, Derwen, Denbighshire (the American 
localities are in the Trenton limestone and Hudson river group). 
Explanation of Figure.—P1. 1. K. fig. 6, left valve, natural size. 
TELLINITES AFFINIS (AZ°Coy). Pl. 1. K. fig. 31. 
fef.—ld. M°Coy, Ann. Nat. Hist. 2nd Series, Vol. VII. p. 51. 
Sp. Ch,—Elliptical, moderately convex ; beaks small, about one-third the length from the anterior end, 
which is elliptically rounded, and with an undefined, obtuse, cardinal slope ; ventral margin nearly straight, with 
a faint shallow sinus in the middle; posterior like the anterior end, rounded elliptically, with sometimes an 
almost imperceptible flexure (as in 7e//ina), extending as a hollow in the left valve from a small sinus beneath 
the posterior end in the margin towards the beak; surface smooth or with a few obtuse marks of growth. 
Length one inch four lines and half, width (from beak to opposite margin) #;, length of anterior end ™, 
depth of valve =. 
This has almost exactly the shape of our recent Tellina radiata, but the minute flexure above alluded to 
is in the longer end, which in that species is the anterior. The species is most allied to the Tellina obliqua 
(Gold.), from the Grauwacke of Ems, from which it differs in being less transverse, in the beaks not being 
mesial, and in the less angularity of the posterior slope; its greater length, less central beaks, and concave 
ventral margin, distinguish it from the Nuculites subemarginatus (Conrad). 
Position and Locality —Rare in the Upper Ludlow rock of Benson Knot, Kendal, Westmoreland. 
Explanation of Figure.—PI. 1. K. fig. 31, left valve, natural size. 
Ath Class. PTEROPODA. 
Turs class is composed of small mollusca which float about in the Northern seas in millions, colouring 
the water for miles, and forming the chief food of whales. They all have a distinct head, furnished with 
tentacula, and a mouth with horny jaws, and a tongue set with hooks, and two large wing-shaped expansions 
from the sides of the neck, from which they derive their name. The mouth is a longitudinal fissure, the 
cesophagus leads to a large globular stomach, from which the intestine takes a few turns, and ends at the 
right side of the neck; their liver is large; respiration is by a vascular net-work on the inside of the mantle, 
from whence the blood is transmitted to a heart of one auricle and one ventricle, from which it is sent to 
the rest of the body through two aorte. The nervous system is much more condensed and approximated 
towards the head than in the bivalves ; a nervous collar surrounds the cesophagus, having two cerebral ganglia 
above, and four on the lower part sending nerves to the viscera and body. They are all hermaphrodite, 
