266 BRITISH PALAZOZOIC FOSSILS. [LAMELLIBRANCHIATA. 
Supposed by Hall to be monomyarian: but where only one adductor is present in a shell, it is always the 
posterior one; and I have detected a large shallow or superficial posterior impression besides the anterior 
muscular impression, which latter is very strong in casts, and often visible as a slight projection externally 
through the thin shell. The byssiferous sinus and oblique depression from it, and the increasing width of the 
posterior end, separate the species, at a glance, from Orthonotus. The name Modiolopsis was proposed by Hall 
(Pal. New York), simply as a substitute for Cypricardites of Conrad, on the grounds that the fossils were 
monomyarian, and therefore more allied to Modiola ; but Modiola is as clearly dimyarian as Cypricardia. 1 
propose, however, to retain the name for such types as the M. modiolaris (Conrad sp.), included by Conrad 
and Hall as part of their respective genera, Cypricardites and Modiolopsis, having the general form and 
byssiferous sinus of Modiola, and agreeing therewith, and with Hdmondia (differing from another section of 
those genera) in having the dorsal margin simple and erect, with a small internal ridge beneath it for the 
internal cartilage. Modiolopsis, as thus restricted, differs from M/odiola in its very strong anterior impression, 
from Sanguinolites in the shorter hinge, which if not straight is convex instead of concave, and the hinge-margin 
being erect instead of inflected to form a concave lunette, containing an external cartilage near the beak, as in 
that genus. 
MoproLopsis? ANTIQUA? (Sow. Sp.) 
Ref. and Syn.—Modiola antiqua (Sow.) Sil. Syst. t. 13. f. 1. 
A specimen probably of this species, but too imperfect for description, is in the collection from the Bala 
schists of Gelli Grin, Bala. 
MODIOLOPSIS COMPLANATA (Sow. Sp.) 
Syn. = Pullastra complanata Sow. Sil. Syst. t. 5. f. 7. 
Sp. Ch_—Oblong, widening to the posterior end, slightly more than twice as long as wide; beaks small 
about one-fifth of the length from the anterior end; anterior end elliptically rounded ; dorsal margin slightly 
elevated ; ventral margin with a slight concavity in the middle, posterior end obliquely subtruncate (at an angle 
of about 50° with the ventral margin), slightly convex, the inferior angle obtusely pointed; sides flattened or 
slightly concave in the middle ; an obtuse diagonal ridge from the beak to the posterior inferior angle ; anterior 
adductor distinct, oval, with a strong, narrow, clavicular, internal ridge, extending from in front of the beak to 
its upper posterior margin; hinge-line half the length from the beak to the posterior inferior end, posterior 
lateral tooth or cartilage plate strong, extending its whole length; surface with small concentric lines of growth. 
AT 
Length eleven and half lines, proportional width from beak to opposite ventral margin 4, width from cardinal 
angle to opposite margin =; (often one-third larger). 
The greater length, more pointed and obliquely truncated posterior end, stronger diagonal ridge, and 
the hollowing of the sides and ventral margin, distinguish this species easily from the Anodontopsis levis 
(Sow. sp.) It varies a little in amount of pointing of the posterior end, rarely being quite so much so as in 
the above-quoted figure. 
Position and Locality—Abundant of small size in the green quartzite (Upper Ludlow rock) of Kirkby 
Moor, Kendal, Westmoreland ; larger in the whitish tilestone of Storm Hill, Llandeilo, Caermarthenshire. 
MoproLopsis INFLATA (A7°Coy). Pl. 1. I. fig. 16. 
Ref—Id. M°Coy, Ann. Nat. Hist. 2nd Series, Vol. VII. p. 58. 
Sp. Ch.—Longitudinally oblong, very gibbous ; beaks obtuse, tumid, incurved, large, close to the anterior end, 
which is large and obtusely rounded ; an obtuse sigmoidal ridge extends from the beak to the posterior inferior 
end, which is elliptically rounded to the very obtuse cardinal angle, which is slightly elevated; the hinge-line 
little more than half the length of the shell, with a slender cartilage ridge just below it; ventral margin very 
slightly concave in front of the diagonal gibbosity. Length one inch six lines, proportional width 4, greatest 
