LAMELLIBRANCHIATA. | LOWER PALAZOZOIC MOLLUSCA. 273 
slope narrow, steeply inclined, separated from the sides by an obtusely rounded ridge; surface apparently 
smooth; about eight radiating hinge-teeth, two long anterior ones, three shorter cardinal ones, and three long 
posterior ones. Length about seven lines; in proportion to length, greatest width (from beaks to opposite margin) 
length of anterior side {,, width of posterior end about =, depth of one valve ;;. 
Position and Locality.—Rare in the schists of Yspatty Evan, N. Wales (the American locality is in the 
shaly sandstone of the Hudson River group, near Rome, Oneida). 
Explanation of Figures.—P|. 1. K. fig. 17. Natural size, left valve ; fig. 17 @, rostral portion magnified 
to shew the diverging teeth and cartilage pits. 
Genus. CLIDOPHORUS (Hail). 
Syn. = Pleurophorus (King).—Etym. «d«dos, a clavicle, &e. 
Gen. Char.—Equivalve, inequilateral, transversely oblong, diagonally gibbous; hinge straight, without 
erenulations, but having an internal cartilage-plate or lateral tooth nearly parallel with it, and a clavicular 
vertical ridge in front of the beak and behind the anterior adductor, both producing deep slits in the cast; in 
some species a small cardinal tooth behind the beak; hinge-margin sharp and erect. 
This genus is clearly allied not to Vucula, but to Modiolopsis. In the Memoirs of the Geological Survey 
this genus is inadvertently made to consist of the shells with crenulated hinge-teeth like Arca, which Hall 
expressly guards against. King’s genus P/eurephorus, I find from examination of authentic specimens to be 
exactly equivalent to Clidophorus. 
CLipopHorus ovaALis (A/"Coy). Pl. 1. K. fig. 7 and 8. 
Reef.—ld. M°Coy, Ann. Nat. Hist. 2nd Series, Vol. VII. p. 55. 
Sp. Ch.—Oval, width two-thirds the length ; anterior and posterior ends almost equal, elliptically rounded ; 
ventral margin gently convex ; valves slightly and evenly convex, the posterior slope very slightly compressed ; 
surface apparently smooth ; clavicular ridge strong, reaching rather more than half way from the beak to the 
ventral margin. Length five lines; proportional width 7. 
This is distinguished from the C. planulatus (Conrad) by its regular oval form, larger and more oblique 
clavicular ridge and less elongation, and from the Cucull@a antiqua (Sow.) by the flatness and oval outline of 
the valves. 
Position and Locality—Plas Madoe, N. of Llanrwst; abundant in the schists, Dolydd Ceiriog Waterfall, 
E. of the Berwyn Mountains. 
Explanation of Figures.—Pl. 1. K. fig.’7. Natural size, right valve ; fig. 8, left valve. 
CLIDOPHORUS PLANULATUS (Conrad Sp.) Pl. 1. K. fig. 9. 
Ref. = Nuculites planulatus and N. scitula (Conrad) fid. Hall, Pal. N. Y. t. 82. f. 9. 
Sp. Ch.—Subelliptical, compressed, greatest width from the beaks to opposite ventral margin ; about twice 
as long as wide; beaks small, rather less than one-third of the length from the anterior end; anterior end 
elliptically rounded; ventral margin gently convex ; posterior end obliquely subtruncate ; hinge-line straight, a 
little shorter than the shell, not elevated; valves uniformly and slightly convex, posterior slope compressed, 
obscurely defined: casts shew a strong oval adductor impression, with the sulcus left by the clavicular ridge, 
extending from the beak to its posterior upper edge exactly half-way to the ventral margin ; a strong posterior 
lateral tooth or cartilage-plate runs nearly to the end of the hinge-line, a little below the simple, erect, cardinal 
margin ; another shorter one runs from the beak to the upper edge of the anterior adductor ; one small oblique 
cardinal tooth in right valve. Length eleven lines, proportional width =, depth of one valve about ;;. 
There seems the most perfect identity of our Welsh and the American species, which is stated by Hall to 
[Fasc. 11.] Nv 
