(1) The oldest part of the shell, the umbo , can be recognized as a large hump on the anterior end of the dorsal side of each shell.(2) The nearly spherical cones have eight to 10 scales, each looking like a shield with a central projection (called an umbo , if you want to impress your botanist or Scrabble-playing friends).(3) In contrast, a strongly obtuse apical angle is associated with an incurved ventral beak that is appressed to the dorsal umbo , resulting in the delthyrium being partly obscured.(4) Argonauta attaches the egg-mass to the umbo of the shell near the dorsal arms, not in the mantle cavity or posterior parts of the shell.(5) A similar pair of umbonal pits occurs in Middle Triassic Gervillia joleaudi (well shown by Niemeyer, 2002, fig.12) as well as in Upper Triassic Gervillancea coxiella.(6) Cyzicus having elongate valves; umbo convex; dorsal margin straight; posterior margin slightly flared; growth bands widely spaced in umbonal region, more closely spaced elsewhere.(7) An umbonate colony is elevated more in the center of the colony than the rise across the surface of the colony.(8) The New Pass specimens differ, however, in having an umbonal angle greater than that of 10 of the 11 specimens of Promysidiella otiosa that were examined in the collections of the Geological Survey of Canada, Ottawa.(9) Below the umbones , the shell margin is folded inward forming a deep lunula and gaping between both valves.(10) Other decorative British products of this period include ‘ umbonate ’ disc brooches.(11) The new species is characterized by a transversely extended, strongly biconvex to globular shell with prominent umbones , relatively numerous costae and a notothyrial cavity supported dorsally by a short median ridge.(12) The umbonal angle narrows while the shape remains mytiliform and the ‘lunule’ (byssal invagination) remains shallow.(13) The developing larval clams are released, preferably in large numbers (saturation spawning) at any time during the veliger stage of development, i.e., the generic stage following the trochophore larval stage and which includes the sub-stages of straight-hinge veliger, umbonate veliger, and pediveliger.(14) M. oreades has a white spore print, adnate, adnexed or even free gills usually white to pale tan in colour, a mid-sized bell-shaped cap but can later become umbonate as it ages.(15) A cap with an umbo is said to be umbonate , as in the two larger mushrooms at the left.(16) Hinge articulation either limited to overlapping shell margins on dorsal side of byssal invagination or consisting of a transposable tooth and socket developed on the umbonal septum.
