Bulletins of American paleontology . ge-form, with three strong radiating plicae. FAMILY ISIYTILTDA];.—^MVTILUS INCRASSATUS. (Fig. 2i3A.)Shell nacreous, tJiick, somewhat intla-ted, marked \vitli concentric lines ofgr\vth ; auteridi margin arched ac-cumiuale; ]H;):^terior Ioaiided, ?ome-wind dilated; uudujiies acute. Jtis lisiially much injured l)y exloiialion and rarely peifect. CUENELLA.—(Fig. 20;Vr>.) Shell small, slu_»rt,^ -• thin. smo()tli in ihcmiddle; hinge, nuir-gin crenulated behindthe ligament. It ap-pears to be rare,thoughit may be owing to its frailness. Mi-ocene. North Carolina
Bulletins of American paleontology . ge-form, with three strong radiating plicae. FAMILY ISIYTILTDA];.—^MVTILUS INCRASSATUS. (Fig. 2i3A.)Shell nacreous, tJiick, somewhat intla-ted, marked \vitli concentric lines ofgr\vth ; auteridi margin arched ac-cumiuale; ]H;):^terior Ioaiided, ?ome-wind dilated; uudujiies acute. Jtis lisiially much injured l)y exloiialion and rarely peifect. CUENELLA.—(Fig. 20;Vr>.) Shell small, slu_»rt,^ -• thin. smo()tli in ihcmiddle; hinge, nuir-gin crenulated behindthe ligament. It ap-pears to be rare,thoughit may be owing to its frailness. Mi-ocene. North Carolina Geol. Sur.: Emmons 193 284 NORTH-CAEOLINA GEOLOGICAL 8TIRVEY. AKCADAE. The valves in tlie Arcadae are equal, regular, and usuallyoblique; the teeth are arranged in long rows, resembling acomb; at the extremes they are longer and frequently curvedor corrugated. AECA LIENOSA.—SAT. (Fig. 204r.) Shell large, inflated, oblique; ribs subequal, numerous,with a groove or channel in the middle; anterior side angu- FiG. lar; lines of growth distinct, giving a striate appearance; theligament area is marked by strong lines diverging from be-neath the umbo; umbones distant; inside margin stronglysulcate or ribbed. It has about 37 ribs. A living shell uponthe Florida coast, but found abundantly in the miocene ofXorth-Carolina. A. SCALARIS. Shell oblong, ovate; ribs twenty-one, strong and trans-versely rugose, ligament area short, transversely marked bylines, and crossing striae parallel to the hinge line. A. INCILE.—SAT. Shell very oblique, sub-quadrangular; anterior side veryshort, posterior sinuate; ribs unequal, stronger on the poste-rior margin; rounded before, angular behind, and much pro- 194 Bulletin 249 north-cakolln^a geological sukvey. 285 Juced; umbones incurved, distant; ligament area crossed bytransverse lines. This shell has about thirty-one principal ribs, with inter-vening raised lines, and transversely marked by lines of growth. A. CENTERAEIA. (Tig. 205.) Sh
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