486 BRITISH PALAZOZOIC FOSSILS. ( LAMELLIBRANCHIATA. 
Position and Locality—Common in dark carboniferous limestone of Lowick, Northumberland; carbo- 
niferous limestone, Derbyshire (with straight ridges). The original Irish locality was Ballygasey, Loughgall co. 
Armagh (very rare). 
Explanation of Figures.—P1. 3. E. fig. 6, from carboniferous limestone of Lowick ; left valve, natural size, 
internal cast, shewing the long cartilage facet (without central pit) along the hinge-margin; also the pallial 
and muscular impressions ; fig. 7, do. var. from Derbyshire, with remarkably straight and regular ridges. The 
radiating ridges are effaced on the ears of this specimen, but by changing the light may be seen as described. 
AVICULOPECTEN GRANOSUS (Soi. Sp.) 
Ref. and Syn. = Pecten granosus Sow. Min. Con, t. 574. f. 2. = Avicula granulosa d’Orb. Prod. p. 135. 
Desc.—Nearly orbicular, slightly oblique, moderately convex in the middle, arching gradually to the 
anterior and front margins, becoming rapidly compressed towards the posterior wing ; apical angle about 125°, 
or 145° including the undefined posterior ear; ears unequal, anterior one small, deeply defined, posterior one 
undefined, extending as far as the margin of the shell. Surface with about forty or fifty tuberculated ribs, 
between each pair of which is usually a smaller one; when the intermediate rib is absent, the spaces are wider 
than the ridges, slightly concave and smooth; they seem deeper and narrower than the ribs, when they are 
alternate in size; usually five tuberculated ridges in the middle of the shell in the space of two lines, at six lines 
from the beak (before the secondary ribs commence). Length two inches, proportional width from beak to 
opposite margin ;\,, length of posterior ear >, depth of left valve 5. 
This species varies considerably in the number of its ridges and in the relative strength of the inter- 
vening ones. 
Position and Locality —Carboniferous limestone of Derbyshire and Lowick. 
AVICULOPECTEN ILLEGALIS (de Kon. Sp.) 
Ref. and Syn. = Pecten plicatus? Phill. Geol. York. t. 6. f. 11. (not Sow.) = Pecten illegalis de Kon. Anim. 
Foss. Belg. t. 4. f. 6. 
Dese.—Suborbicular, moderately convex, most so at one-third the width from the beak; ears flattened, 
strongly defined from the body of the shell; anterior ear abruptly defined by a narrow, nearly vertical sharp- 
edged slope, slightly arching forwards and upwards in the old shell; anterior ear obtuse, with a slightly sigmoid 
margin, parallel to which it is coarsely striated; posterior ear faleately pointed, extending slightly beyond the 
posterior margin of the shell, strongly striated, parallel with the posterior edge, defined by a rather rapid slope; 
no radiating ridges on either of the ears; apical angle about 105°; body of the shell with about forty coarse, 
rounded, subalternate ribs, separated by much narrower spaces, nearly equal at the margin at one inch long, 
where there are about six in three lines; one half of the ridges extend only within four lines of the beak; one 
half of the remainder disappearing at about two lines from the beak; surface crossed by few inconspicuous, 
minute lines and waves of growth. Length one inch two lines, proportional width from beak to opposite 
margin ~, length of posterior ear about =, depth of left valve =, (left valve only described). 
This shell bears some slight resemblance to the Pecten plicatus of Sowerby, but has coarser and more 
regular ribs, no marked obliquity, and unradiated ears. These are the characters on which M. de Koninck 
mainly establishes his Peeten illegalis, referring to the Pecten plicatus? of Phillips. The figure which he gives 
does not bring out the inequality of the ridges, which however he mentions, and Phillips’s figure imperfectly 
shews. Both figures represent the posterior ear rather less pointed than it is in nature. The species is much 
smaller than the A. docens, and at the same distance from the beak has the ribs much coarser, fewer in number 
in a given space, and more unequal: the radiation of the ears is also different. 
Position and Locality.—Rare in the carboniferous limestone of Malham Moor. 
