258 BRITISH PALAXOZOIC FOSSILS. [ LAMELLIBRANCHIATA. 
cartilage external, linear, simple, placed on a narrow marginal facet extending from the beak more or less 
towards the anal angle ; Ainge edentulous or with two small cardinal teeth beneath the beak in one valve, and 
one in the other, and a long, slender, posterior, bifid, lateral tooth in each; substance corneo-caleareous, lamellar 
without, pearly within. 
The subgenus Meleagrina (Lam.) differs in its rotundato-quadrate form, undefined posterior wing, and 
the ligamentary or cartilage facet broadly dilated beneath and behind the beak, and the small anterior, retractor, 
muscular impressions, numerous, forming a vertical row from the beak towards the ventral margin. The two 
following species are referred with doubt to this genus, their internal characters being imperfectly known. 
Avicuta Dansyi (M°Coy). PI. 1.1. figs. 11 to 15. 
Ref—Id. M°Coy, Ann. Nat. Hist. 2nd Series, Vol. VII. p. 59. 
Sp. Ch.—Obliquely ovate, anterior end broadly rounded, posterior end more or less narrowed, rounded ; 
ventral margin evenly convex; hinge-line rather less than half the width of the shell; posterior wing scarcely 
twice the length of the anterior ; both wings nearly rectangular, with slightly concave margins; left valve gently 
convex, most gibbous near the beak, marked with minute concentric, irregular, interrupted strize and wrinkles, 
crossed by a variable number of obtuse ridges radiating from the beak, and generally becoming obsolete towards 
the margin; right valve flat, with slight irregular concentric wrinkles and striz of growth, without radiating 
ridges. Average length from anterior to posterior margin 2 inches 3 lines, proportional width at right angles 
to middle of hinge line & to &, length of hinge line including both ears = to =. 
This species varies much in the amount of its obliquity and transverse elongation, and the radiations of 
radiation on the left valve: these latter resemble the radiations of Pholadomya, for which that valve might be 
taken when the ears are concealed. Traces of a subcentral muscular impression occasionally visible. Some of 
the varieties are so slightly oblique as to assume a rotundato-quadrate form. Traces of two fine internal ridges 
diverging from the beak of the flat valve where the wings join the body of the shell (resembling those of Pecten). 
Mr Salter has suggested the specific name to me for this species in honour of one who first collected 
it, together with most of the other fossils of Kendal. 
Position and Locality—V ery abundant in the greenish Upper Ludlow quartzites of Benson Knot, Kendal, 
Westmoreland. 
Explanation of Figures.—P\. 1.1. fig. 11. Small quadrate specimen of the convex, radiated, or left valve ; 
fig. 12, orbicular variety, natural size; figs. 13 and 14, obliquely elongate varieties; fig. 15, unradiated, flat, or 
right valve, natural size. 
AVICULA? ORBICULARIS. Var. (Sow.) 
Ref —Sil. Syst. t. 20. f. 3. 
Sp. Ch.—Obliquely ovate, evenly gibbous, most so a little in front of the middle; posterior and ventral 
margins forming one broad elliptical curve ; dinge straight, shorter than the shell, cardinal angle 115°; no 
defined wing nor posterior slope; anterior lobe compressed (?rounded), deeply defined from the body of the 
shell; surface marked with imbricating lines and waves of growth. Length from beak to posterior end two 
inches three lines; greatest proportional width, from middle of hinge-line to ventral margin 7; depth of one 
valve =. 
There seems an obscure trace of an internal, slender, cartilage plate, extending considerably below the 
hinge-margin, indicating an affinity with Modiolopsis; but the imperfection of the specimen leaves me uncertain 
of its true generic position, and I therefore leave it as placed by Mr Sowerby, without thinking it really an 
Avicula. 
Position and Locality—Fine Caradoc sandstone of Acton Scott, Church Stretton, Shropshire. 
Genus. PTERINEA (Gold.) 
Gen. Char —Transversely trigonal, oblique, inequivalve*, left valve most convex, very inequilateral, beaks 
* Goldfuss says equivalve, but, I am convinced, erroneously. 
